All valuable points, and I accept all that.
My POV is a business perspective here, since ultimately money should drive the site's ability to grow (conversely, the lack will see it wither). I have not yet found the funds to become a supporter, but if I found the value proposition better I'd probably have made it happen by now. It's not excessive, but the fact that I have played for a few years for free tells me something.
What percentage of users are Supporters? I'm guessing it's not near high enough.
What percentage of caught cheaters are Supporters? I'm guessing it's low. If you invest in the growth of a game that has no payout, chances are you'll care more about its integrity.
I have played a sim baseball game for 10 years and I keep renewing my teams. I am a commissioner and help in many ways. I am invested, in both time and money, in seeing the game work well. I see a large number of active, helpful owners/mods here, and they are similarly invested.
Just my opinion, but I think that group would expand if Supporter carried the option of helping smaller nations prosper. I think it's a win-win for the nations and the game as a whole. Plus, did I mention more income? That can't hurt, can it?