Welp, I had planned on this being a bit of a progress thread, however since posting I have done a grand total of zero of the things on the list.
However, I have just placed an order for a mosfet RR kit from roadstercycle.com - now trying to find a suitable aftermarket starter relay (this looks promising:
https://www.wemoto.com/parts/picture/hl-714979). Anyone tried this or something similar?
I've been in touch with a UK-based chap who makes the starter circuit wiring upgrade at a much more reasonable rate than motoelectric - hoping he can put together a kit at some stage, though I don't think I'm in a rush for that yet.
Moving into a new house end of next week (as long as the solicitors come to an agreement today or tomorrow!), then I can get to work on it in earnest and at least get the RR & Relay done (and hopefully hook up the new headlight).
In other non-Monster news, I've purchased the frame/engine/tank of a '73 Suzuki GT550 triple as the basis of a new project. Besides the Monster, I'm a big fan of two-strokes ��
Itching to get back out there riding!