Though I like the spirit behind this idea, I don't think it's necessary and I'm not sure it would help.

Given enough time--and merit sources awarding merit to good users, ones who aren't merit farmers--this problem should take care of itself.  The merits sent back and forth between alt accounts of idiots & merit dealers should eventually run out, leaving them and the forum as a whole with less over time.

Aside from that, I'm pretty sure that when Theymos rolled out the merit system in January, it was pretty well-thought out and he's probably not going to be tweaking it anytime soon.  We're still early on with this feature, so the verdict isn't in whether it's a failure or not.  So far it doesn't seem to have caused a pullback on shitposts (I continue to see a lot of them), but users who make them don't seem to be earning much merit and hence they won't rank up.  That removes a lot of the financial incentive for them to continue to make them.  Right now, that's good enough for me.