Swing arm bushings are not high RPM nor are they high temp. A lot of people use plastic (delrin or something of the like) for swing arm bushings. It is not at all uncommon.
As far as differentials, axle tubes, combined sprockets/diffs... Umm, no, nah, and absolutely not, lol. We're not re-inventing the wheel here. This machine is awesome and works great. You're talking about some very serious, unwarranted modifications that in the end are going to change the handling characteristics drastically on a machine of which I'm quite fond of how it handles now. I have zero desire to have a differential or start modifying things that work perfectly fine. Very simply, very easily, very cheaply, with very little effort and time, I'm going to replace my metal-to-metal OEM Honda roller swing arm bearings with a delrin bushing, which has give, which is all I need. They're worn out and need replacing anyways. Rube Goldberg was certainly interesting but nary effective.
Yup you got it with the vibration. It's a really big single cylinder, and you feel that at low RPM. And you do know what I'm talking about with the rubber sprocket mount. So unfortunately those are not available for my application.
I'm glad you're confident in me helping with building a harness, at least one of us is, haha! If you think it can be done I'll try. If it can clean this pig up a bit that would be nice. I'm just uncertain if there are things which could be left out. If you made a new harness, if it's just as big and bulky, that's might not solve that much. Sure it would be nice to have a nice new harness, but this one does still work. It just needs a diet or something, lol. I don't know.