But who's going to filter out the good AI contributions from the bad AI trolls and bargain-bin-model slop?

With AI there is an infinite stream of contributions to curate. No human is ever going to volunteer for that, so unless you keep AI contributions very tightly restricted you'll rapidly lose all human contributors. At which point nobody is left to ensure only good contributions get in, so it is only a matter of time before it devolves into a giant pile of crap.

Besides, who's going to pay to run those AIs? Good models aren't free, so you are effectively turning it into a pay-to-win project. You can be absolutely certain that some tech billionaires are going to burn a few million to have "good AI" constantly rewrite their pages the way they want it.