I've made my suggestion to a solution to a problem diagnosed by others.

It could work.

Indeed if the 'moderated off-topic' was treated was a fresh new board and the old off topic continued unmoderated the new board would be easier to moderate because all the content there would be new and all the years of old content would remain unmoderated.

If it were bound by the same rules as the rest of the boards, people posting there would know exactly were the stood before posting there.

In my personal opinion it's the best of both worlds.