John
It's obviously an insane problem!
When you type these diskpart commands, you avoid to assign drive letter to new volumes (automount) and you flush all the old and unused volumes (scrub).
You can see that it doesn't remove your actual HD drives, so, by using in a certain way, you can get a chance to still assign letters to your USB drives.
If you don't run automount commands, Windows will assign a letter to VMFS volumes, there's still a chance to correct this by running FD commands on ESX.
Insert and manually assign, one by one, your USB drives, and don't run automount scrub, it will erase all parameters for your USB sticks. Normally when you'll plug one of this USB stick it will be recognized and mounted.
If you experience too many issues with this, you should use something like "USB everywhere" which permits you to see a USB device as a network drive. Normally I won't recommend you to add a network path to reach your repository, but since you're running USB and it's a slow storage type to back up, from my personal opinion.
Finally, if you don't want to get issues with automount, you can use the "virtual appliance" mode, means Veeam into VM, which doesn't need to present LUNs, because it uses the ESX VMFS connection. But now, it will complicate the USB mount into VM!
