Good point about Discord's TOS – that could be a problem.
Glad to hear you like the Donator Rank idea.
I hear you about early access, too. The goal isn't to delay updates for the majority but rather to offer a little sneak peek to donators. It would just be a bot that compiles every commit on master and puts that somewhere that donators could access.
Now, the pay-what-you-want model is a very interesting idea! It's like a soft paywall that's intentionally easy to bypass for those who can't or don't want to pay, while still creating a perception of "buy the thing or pirate it" instead of "use the free thing and maybe donate". I think that perception could make quite a difference.
Of course, it's a pretty major change to go from a mainly ad-supported model to a paid-but-easy-to-pirate one, and I'd definitely want to run some tests before committing to it, but I think this system could turn out to be very effective and is worth experimenting with.
I might try it on Wolfram or ForgeWurst first and see what the response is there.