Well, I did some testing....
It's possible to integrate USB drivers into a WinPE boot.wim image.
Though I'm not sure how effective they would be. To boot from a USB device requires the BIOS/UEFI to support USB booting. That means there's an IDE-translation layer built into the BIOS which makes it appear to the OS that the USB device is a pseudo-IDE device.
As a test, I integrated the current x64 DriverPack Chipset into a vanilla WinPE x64 boot.wim.
DriverPack Chipset x64 contains 221 .inf driver files.
Of those 221, DISM only integrated 154 and ignored the rest.
I haven't checked thoroughly, but it appears that all the USB .inf files were successfully integrated.
The missing ones are probably from the "Vista" folder.
So while it's possible to integrate USB3 into a boot.wim, I still maintain that it's not recommended. Unless someone can prove that there is a distinct benefit to do so AND post benchmarks to prove the drivers are utilized for a speed boost.
Here's the relevant section of the DISM log:
** Listing all 3rd party drivers in index 1
Deployment Image Servicing and Management tool
Version: 6.1.7600.16385
Image Version: 6.1.7600.16385
Obtaining list of 3rd party drivers from the driver store...
Driver packages listing:
-------------- | ------------------ | ----- | ---------- | ------------------------------ | ---------- | -------------
Published Name | Original File Name | Inbox | Class Name | Provider Name | Date | Version
-------------- | ------------------ | ----- | ---------- | ------------------------------ | ---------- | -------------
oem0.inf | 2008s4el.inf | No | System | Intel | 2/2/2009 | 9.1.0.1012
oem1.inf | 5000xzvp.inf | No | System | Intel | 2/20/2008 | 8.6.0.1002
oem10.inf | 965g.inf | No | System | Intel | 8/31/2007 | 8.3.0.1016
oem100.inf | pbo-core.inf | No | System | Intel | 7/29/2009 | 8.8.0.1014
oem101.inf | pbo-usb.inf | No | USB | Intel | 7/29/2009 | 8.8.0.1014
oem102.inf | heci.inf | No | System | Intel | 6/23/2009 | 4.2.0.1008
oem103.inf | heci.inf | No | System | Intel | 7/9/2007 | 2.1.22.1033
oem104.inf | heci.inf | No | System | Intel | 9/18/2009 | 3.2.20.1046
oem105.inf | heci.inf | No | System | Intel | 6/23/2009 | 5.2.0.1008
oem106.inf | heci.inf | No | System | Intel | 9/17/2009 | 6.0.0.1179
oem107.inf | mesrl.inf | No | Ports | Intel | 9/17/2009 | 6.0.0.1179
oem108.inf | mesrle.inf | No | Ports | Intel | 9/17/2009 | 6.0.0.1179
oem109.inf | heci.inf | No | System | Intel | 9/22/2011 | 7.1.21.1134
oem11.inf | 965m.inf | No | System | Intel | 10/19/2007 | 8.3.1.1005
oem110.inf | mesrl.inf | No | Ports | Intel | 9/11/2010 | 7.0.0.1109
oem111.inf | mesrle.inf | No | Ports | Intel | 9/11/2010 | 7.0.0.1109
oem112.inf | heci.inf | No | System | Intel | 11/9/2011 | 8.0.0.1262
oem113.inf | mesrl.inf | No | Ports | Intel | 11/9/2011 | 8.0.0.1262
oem114.inf | nfsmb64.inf | No | System | NVIDIA | 3/22/2010 | 4.7.9.0
oem115.inf | smuc64.inf | No | System | NVIDIA | 6/29/2009 | 5.1.2600.171
oem116.inf | smuc64.inf | No | System | NVIDIA | 3/22/2010 | 5.1.2600.208
oem117.inf | asmthub3.inf | No | USB | ASMedia Technology Inc | 2/21/2012 | 1.14.8.0
oem118.inf | asmtxhci.inf | No | USB | ASMedia Technology Inc | 2/21/2012 | 1.14.8.0
oem119.inf | etronxhci.inf | No | USB | Etron Technology Inc. | 4/23/2012 | 1.0.0.112
oem12.inf | cdvcore.inf | No | System | Intel | 7/12/2010 | 9.2.2.1031
oem120.inf | flxhcic.inf | No | USB | Fresco Logic | 4/12/2012 | 3.5.46.0
oem121.inf | flxhcih.inf | No | USB | Fresco Logic | 4/12/2012 | 3.5.46.0
oem122.inf | ftdibus.inf | No | USB | FTDI | 3/18/2011 | 2.8.14.0
oem123.inf | ftdiport.inf | No | Ports | FTDI | 3/18/2011 | 2.8.14.0
oem124.inf | nusb3hub.inf | No | USB | Renesas Electronics | 9/13/2011 | 2.1.27.0
oem125.inf | nusb3xhc.inf | No | USB | Renesas Electronics | 9/13/2011 | 2.1.27.0
oem126.inf | cbaf.inf | No | USB | Intel Corporation | 8/28/2007 | 1.4.22.0
oem127.inf | hwa.inf | No | USB | Intel Corporation | 9/29/2008 | 1.1.6.0
oem128.inf | uwbdfu.inf | No | USB | Intel Corporation | 6/13/2008 | 1.1.6.0
oem129.inf | uwbusb.inf | No | USB | Intel Corporation | 6/13/2008 | 1.1.6.0
oem13.inf | cougahci.inf | No | hdc | Intel | 9/10/2010 | 9.2.0.1011
oem130.inf | rusb3hub.inf | No | USB | Renesas Electronics | 9/15/2011 | 3.0.8.0
oem131.inf | rusb3xhc.inf | No | USB | Renesas Electronics | 9/15/2011 | 3.0.8.0
oem132.inf | ser2pl.inf | No | Ports | Prolific | 4/29/2011 | 3.3.17.203
oem133.inf | tihub3.inf | No | USB | Texas Instruments Incorporated | 5/2/2012 | 1.12.24.0
oem134.inf | tixhci.inf | No | USB | Texas Instruments Incorporated | 5/2/2012 | 1.12.24.0
oem135.inf | amdhub30.inf | No | USB | Advanced Micro Devices | 1/3/2012 | 1.0.0.72
oem136.inf | amdxhc.inf | No | USB | Advanced Micro Devices | 1/3/2012 | 1.0.0.72
oem139.inf | usbfilter.inf | No | USB | Advanced Micro Devices Inc. | 12/14/2011 | 2.0.7.176
oem14.inf | cougcore.inf | No | System | Intel | 11/20/2010 | 9.2.0.1016
oem141.inf | usbfilter.inf | No | USB | Advanced Micro Devices Inc. | 11/29/2010 | 1.0.18.119
oem142.inf | smbusamd.inf | No | System | Advanced Micro Devices, Inc | 4/15/2010 | 5.12.0.13
oem143.inf | sisagp.inf | No | System | SiS | 4/23/2008 | 7.2.0.1230
oem144.inf | viahub3.inf | No | USB | VIA | 11/14/2011 | 6.1.7600.1803
oem145.inf | xhcdrv.inf | No | USB | VIA | 11/14/2011 | 6.1.7600.1803
oem146.inf | viaagp1.inf | No | System | VIA Technologies, Inc. | 9/23/2005 | 5.2.0.3450
oem148.inf | usbfilter.inf | No | USB | Advanced Micro Devices Inc. | 12/17/2010 | 1.0.20.122
oem149.inf | sisagp.inf | No | System | Silicon Integrated Systems | 4/14/2010 | 7.2.0.1232
oem15.inf | coughaud.inf | No | System | Intel | 7/19/2011 | 9.2.0.1032
oem150.inf | iusb3hcs.inf | No | System | Intel | 5/21/2012 | 1.0.5.235
oem151.inf | iusb3hub.inf | No | USB | Intel(R) Corporation | 5/21/2012 | 1.0.5.235
oem152.inf | iusb3xhc.inf | No | USB | Intel(R) Corporation | 5/21/2012 | 1.0.5.235
oem153.inf | viahub3.inf | No | USB | VIA | 1/20/2012 | 6.1.7600.1902
oem154.inf | xhcdrv.inf | No | USB | VIA | 1/20/2012 | 6.1.7600.1902
oem16.inf | cougheci.inf | No | System | Intel | 4/14/2011 | 1.2.0.1030
oem17.inf | cougide.inf | No | hdc | Intel | 9/10/2010 | 9.2.0.1011
oem18.inf | cougme.inf | No | System | Intel | 4/14/2011 | 1.2.0.1030
oem19.inf | cougsmb.inf | No | System | Intel | 9/10/2010 | 9.2.0.1011
oem2.inf | 5400.inf | No | System | Intel | 1/30/2008 | 8.6.1.1001
oem20.inf | cougusb.inf | No | USB | Intel | 12/21/2010 | 9.2.0.1021
oem21.inf | couide2.inf | No | hdc | Intel | 9/28/2010 | 9.2.0.1014
oem22.inf | dh89xxcc-ahci.inf | No | hdc | Intel | 3/10/2011 | 9.2.2.1020
oem23.inf | dh89xxcc-cor.inf | No | System | Intel | 3/10/2011 | 9.2.2.1020
oem24.inf | dh89xxcc-id2.inf | No | hdc | Intel | 3/10/2011 | 9.2.2.1020
oem25.inf | dh89xxcc-ide.inf | No | hdc | Intel | 3/10/2011 | 9.2.2.1020
oem26.inf | dh89xxcc-smb.inf | No | System | Intel | 3/10/2011 | 9.2.2.1020
oem27.inf | dh89xxcc-usb.inf | No | USB | Intel | 3/10/2011 | 9.2.2.1020
oem28.inf | dmi_pci.inf | No | System | Intel | 11/7/2008 | 7.0.1.1011
oem29.inf | e5100.inf | No | System | Intel | 4/30/2008 | 8.6.1.1002
oem3.inf | 852.inf | No | System | Intel | 8/25/2003 | 5.1.0.1006
oem30.inf | e7220.inf | No | System | Intel | 1/10/2005 | 7.0.0.1011
oem31.inf | e7230.inf | No | System | Intel | 2/22/2006 | 8.1.0.1002
oem32.inf | e7300.inf | No | System | Intel | 1/30/2008 | 8.6.1.1001
oem33.inf | e7520.inf | No | System | Intel | 3/9/2006 | 7.3.0.1013
oem34.inf | e8500.inf | No | System | Intel | 9/13/2005 | 7.2.2.1001
oem35.inf | esb2id2.inf | No | hdc | Intel | 1/30/2008 | 8.6.1.1001
oem36.inf | esb2ide.inf | No | hdc | Intel | 6/28/2008 | 9.1.1.1003
oem37.inf | esb2usb.inf | No | USB | Intel | 11/7/2008 | 7.4.1.1005
oem38.inf | g33q35.inf | No | System | Intel | 1/30/2008 | 8.6.1.1001
oem39.inf | ibexahci.inf | No | hdc | Intel | 6/8/2010 | 7.0.0.1013
oem4.inf | 855.inf | No | System | Intel | 10/11/2002 | 4.20.1007.0
oem40.inf | ibexcore.inf | No | System | Intel | 10/28/2009 | 9.1.1.1022
oem41.inf | ibexid2.inf | No | hdc | Intel | 9/17/2009 | 9.1.1.1027
oem42.inf | ibexide.inf | No | hdc | Intel | 6/4/2009 | 9.1.1.1013
oem43.inf | ibexsmb.inf | No | System | Intel | 6/8/2010 | 1.0.0.2
oem44.inf | ibexusb.inf | No | USB | Intel | 8/20/2009 | 9.1.1.1020
oem45.inf | ich5core.inf | No | System | Intel | 1/10/2005 | 7.0.0.1011
oem46.inf | ich5id2.inf | No | hdc | Intel | 11/15/2006 | 8.2.0.1011
oem47.inf | ich5ide.inf | No | hdc | Intel | 11/15/2006 | 8.2.0.1011
oem48.inf | ich5usb.inf | No | USB | Intel | 9/13/2006 | 8.2.0.1008
oem49.inf | ich6core.inf | No | System | Intel | 1/10/2005 | 7.0.0.1011
oem5.inf | 865.inf | No | System | Intel | 3/25/2004 | 5.1.0.1009
oem50.inf | ich6id2.inf | No | hdc | Intel | 11/15/2006 | 8.2.0.1011
oem51.inf | ich6ide.inf | No | hdc | Intel | 11/15/2006 | 8.2.0.1011
oem52.inf | ich6usb.inf | No | USB | Intel | 9/13/2006 | 8.2.0.1008
oem53.inf | ich78id2.inf | No | hdc | Intel | 8/5/2009 | 9.1.1.1016
oem54.inf | ich78ide.inf | No | hdc | Intel | 8/5/2009 | 9.1.1.1016
oem55.inf | ich78usb.inf | No | USB | Intel | 8/5/2009 | 9.1.1.1016
oem56.inf | ich7core.inf | No | System | Intel | 8/5/2009 | 9.1.1.1016
oem57.inf | ich8core.inf | No | System | Intel | 2/20/2008 | 8.6.1.1002
oem58.inf | ich9core.inf | No | System | Intel | 1/21/2009 | 9.1.1.1013
oem59.inf | ich9usb.inf | No | USB | Intel | 12/3/2008 | 8.3.1.1011
oem6.inf | 915.inf | No | System | Intel | 3/10/2005 | 7.0.0.1019
oem60.inf | ichacore.inf | No | System | Intel | 1/21/2009 | 9.1.0.1013
oem61.inf | ichausb.inf | No | USB | Intel | 2/25/2008 | 9.0.0.1005
oem62.inf | ichxdev.inf | No | System | Intel | 11/7/2008 | 7.1.1.1011
oem63.inf | intelcp2.inf | No | System | Intel | 10/28/2009 | 9.1.1.1022
oem64.inf | intelcpu.inf | No | System | Intel | 12/3/2008 | 9.1.0.1010
oem65.inf | intelioh.inf | No | System | Intel | 2/8/2010 | 9.1.1.1026
oem66.inf | ioatdma.inf | No | System | Intel | 8/14/2008 | 1.2.67.0
oem67.inf | ivybridg.inf | No | System | Intel | 8/26/2011 | 9.3.0.1011
oem68.inf | jaketown.inf | No | System | Intel | 7/19/2011 | 9.2.3.1018
oem69.inf | jasperfo.inf | No | System | Intel | 11/4/2009 | 9.1.2.1004
oem7.inf | 915m.inf | No | System | Intel | 5/26/2004 | 6.1.0.1008
oem70.inf | nehalmex.inf | No | System | Intel | 1/11/2011 | 9.1.2.1014
oem71.inf | pantahci.inf | No | hdc | Intel | 8/26/2011 | 9.3.0.1011
oem72.inf | pantcore.inf | No | System | Intel | 1/11/2012 | 9.3.0.1020
oem73.inf | pantid2.inf | No | hdc | Intel | 8/26/2011 | 9.3.0.1011
oem74.inf | pantide.inf | No | hdc | Intel | 7/15/2011 | 9.3.0.1008
oem75.inf | pantsmb.inf | No | System | Intel | 8/26/2011 | 9.3.0.1011
oem76.inf | pantusb.inf | No | USB | Intel | 8/26/2011 | 9.3.0.1011
oem77.inf | pantusb3.inf | No | System | Intel | 10/14/2011 | 9.3.0.1018
oem78.inf | patahci.inf | No | hdc | Intel | 3/16/2011 | 9.2.3.1013
oem79.inf | patcore.inf | No | System | Intel | 6/8/2011 | 9.2.3.1016
oem8.inf | 945.inf | No | System | Intel | 2/6/2007 | 8.3.0.1011
oem80.inf | pathaud.inf | No | System | Intel | 3/16/2011 | 9.2.3.1013
oem81.inf | patid2.inf | No | hdc | Intel | 3/16/2011 | 9.2.3.1013
oem82.inf | patide.inf | No | hdc | Intel | 3/16/2011 | 9.2.3.1013
oem83.inf | patsheci.inf | No | System | Intel | 6/8/2011 | 1.2.3.1016
oem84.inf | patsmb.inf | No | System | Intel | 3/16/2011 | 9.2.3.1013
oem85.inf | patusb.inf | No | USB | Intel | 3/16/2011 | 9.2.3.1013
oem86.inf | pm45gm45.inf | No | System | Intel | 6/28/2008 | 9.1.0.1003
oem87.inf | qd3nodrv.inf | No | System | Intel | 1/15/2008 | 1.3.0.0
oem88.inf | snb2009.inf | No | System | Intel | 3/10/2011 | 9.2.0.1026
oem89.inf | tcreek.inf | No | System | Intel | 9/10/2010 | 9.1.2.1010
oem9.inf | 945gm.inf | No | System | Intel | 5/18/2007 | 8.3.1.1005
oem90.inf | tcrkahci.inf | No | hdc | Intel | 9/10/2010 | 9.1.2.1010
oem91.inf | tcrksd.inf | No | SDHost | Intel | 11/12/2010 | 9.1.2.1011
oem92.inf | tcrkusb.inf | No | USB | Intel | 10/8/2010 | 9.1.2.1012
oem93.inf | whed_dev.inf | No | System | Intel | 8/7/2009 | 9.1.1.1016
oem94.inf | whtpi2c.inf | No | System | Intel | 12/21/2010 | 9.2.2.1015
oem95.inf | whtpi2c2.inf | No | System | Intel | 3/27/2011 | 9.2.2.1023
oem96.inf | whtpoint.inf | No | System | Intel | 11/30/2010 | 9.2.2.1016
oem97.inf | whtptsd.inf | No | SDHost | Intel | 10/12/2010 | 9.2.2.1009
oem98.inf | wptahci.inf | No | hdc | Intel | 10/12/2010 | 9.2.2.1009
oem99.inf | wptusb.inf | No | USB | Intel | 3/27/2011 | 9.2.2.1022
The operation completed successfully.