I'd have one acheivement for each time you gain a rank. I'd also have an acheivement for getting a merit, then when you get that one it unlocks an acheivement for getting 5, and it increases the more you get it. Another would be to have 2000 non reported posts, and every reported post sets you back 10. Then, if they had enough people, they could have a recommend acheivement tab for games, and the AG people could check it out, but only 3 acheivement suggestions sent in for each day. I would love if they made a few VERY hard ones, like that one suggested earlier, for alot of boxhead kills, but not that many. Maybe around 1,000 devil kills.
I think you should get an achievement by beating a game, advancing ranks, and earning merits. It would make the experience so much more worthwhile, especially beating a game.