Yes, that'd work. But if you're going to go the VM route, I don't think you need to bother with a hardware keyboard broadcaster - the functionality of feeding input from 1 keyboard into multiple VM's simultaneously already exists within the VM utilities.

If we can use a $35 KM synchronizer to feed multiple WoW clients without a lot of other tools, that could become a great option for people that don't want to deal with multiple PC's or multiple VM's.