I use those wedge locking nordlock washers on my hub motor e-bikes. They work great, I had problems with motors loosening up without them because motor torque and brake torque tried to twist the hub in opposite ways. I’ve never had one loosen since adding a Nordlock.
I don’t think they can add friction though, which is what you need in this case.
Painter/builder Keith Anderson made really cool stainless inserts that slide into plate dropouts and give you stainless on all surfaces that the axle touches. They also were impossible to mis-align. I have the longer ones for horizontal or track drops that I’ll never use and would see if they are interesting to anyone. I’ll put an ad in the forsale.
