IMO, they'd need to be given out manually to avoid the spamming of the requirements. not achievements in that sense, but trophies. (no, not psn achievements)
mainly would be given out at the tbt yearly awards, and obviously could be given out at a moderator/admin's discretion, so long as that doesn't promote being a suck-up.
also, nook, note i wasn't active at the time when it was suggested. and i too would be against spammy achievements, but a nice little reminder of what the member has done for the community wouldn't hurt, imo.