There is nothing terribly complicated there. It's just an AC motor ("brushless DC") with a classic 3-phase inverter and a resolver. There are plenty of companies that make controllers for this kind of setup. Granted, they are typically not powerful enough for SOTA drivetrains, but it's a question of time.

Power electronics will need to fit into the footprint of the e-axle. Or maybe you'll need to manufacture a new housing. Both are easily doable for small companies.

> VW and Kia/Hyundai EVs were found to use custom dimensions motor bearings that can't be bought on the open market from anywhere, so only the OEM and their dealers can get them via their supply chain.

Again, an independent manufacturer can easily make them.