It is not hard at all, I mean people have been traveling to the moon for quit some time, sooo.....
It is all about how much effort one should put into it. If I needed them my self they would have been available already
Ref standard collet, the threads are the same on the SG shaft, it just has to be chopped off, no big deal, and as you say a shorter flywheel.
The main issue today is that most things has become rather expensive compared to what it was just a few years back, and many people invest a lot less in modelhobby. And, making custom parts in low quantities.... Well,