Wow, that end play link shows that's not much there to scavenge. It does look like it would be pretty straight forward to just replace the motor though.

My problem with Dremel's is they just don't have enough uumph for me and everything I try to do with it loads it down so much I get scared it's going to burn up on me. My go to at work where there was a huge compressor was a small air die grinder. But you need a good sized compressor for the beast. Through HF they are only like $14, but you need a $500++ compressor to run it for any time.

HF also has a long shaft electric die grinder that is awesome. I have two them, but they are much more bulky but they go at 22,000 rpm and I just can't load them down they have so much power.

Have you though of one of those cable drive units that are powered by a bench grinder? I don't know if the limiting factor is cable or the fact it only rotates at 3400rpm, or the cable is too short.