I have done some CNC conversions using VFD's to run 3-phase spindle and coolant motors. eBay VFD's have been inexpensive and have worked well. One issue that has come up, has been low speed torque. Most VFD's can be tuned to improve low speed torque, but usually, I have to allow for a practical range starting at 30% of full motor speed. Also I have had a hard time running spindle motors above 60 Hz because they aren't usually balanced very well. This is frustrating because the VFD's I have can go up to 400 Hz. It would be nice to have the increased range. The higher frequencies will also produce more heat, so even if a motor is well balanced, there may still be a significant RPM limit.
VFD's vary in how they operate. I believe some may be able to use DC on their inputs, but some won't.
Bottom line,I think the low speed torque is the deal breaker for VFD's with 3-phase induction motors on EV's.
I could be wrong, though.