Thanks for the suggestion. I think this could be implemented using PayPal's Authorization & Capture API (there's also a guide here), that way we don't actually take money out of people's accounts long before providing them a service.
But I'm not responsible for anything money related including the toplist system, so this is something that @ccw would have to look into and implement.
Hmmm. Theoretically we could do this -- and allow the server to choose whether or not to enable addons.
I'm not sure how to feel about it, but I'm not entirely averse.
I recommend you to post a GitHub issue with your addon suggestion so that you can get more feedback
Yes, I agree that the widescreen fix should be in MTA. I've milestoned your issue as 1.6 — this doesn't necessarily mean it WILL come in 1.6, just means that it forces someone to look at it sooner rather than basically never.
For other fixes you should file separate issues.
But stuff like SkyGFX will 99% not be accepted because it's more than just a bug fix