As the person who put the system in place, I think your suggestion are good ones and doable. I'd have to look into it after I'm done with changing the front page hardware chart. Here's my thoughts on each proposition:
1) I think there's an option to do with PayPal (which we use for the supporter program), although I'd have to check with other admins if we want to go down that route. If we work on your other points an auto-renew option might not be needed
2) That could be easily doable, I'd have to check with @Machina about the pricing model we'd use for longer terms.
3) While I'm not a fan of popups, I think a reminder before expiry could be useful. We could change the "Active VCG Supporter" button in the top menu to display the number of days left when a subscription is say under 20 days from running out and the background color could change as you get closer to the end.
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