It could be worth considering once the series is out, a containment board would offer any newfags g5 brings in a better place than 4chin and so raise the overall site userbase. with a bit of luck they might find interest in g4 too and from what i can tell a majority of the screeching on /mlp/ is due to the mixing of both in certain threads.
On the other hand it could also invite trolling and posting of g5 art on fim board and make moderation a pain in the ass for everyone.
Still, i think the idea shouldn't be dismissed without giving it a thought.
as questionable as the designs are they do have hooves