GW is a model company, not a rules company.
Therefore, I don't have any issue with people using any models whatsoever to play the game that is not their primary focus, and figure no organizer should either.
In a basic game balance sense I would like them to be of fairly appropriate size (albeit, I still run old Ork Trukks, so maybe I should zip my lip) At around 3-3.5 they're a touch on the weedy side.
I'd really likely have no issues whatsoever, and if they have a nice paint job and match the look of the rest of the army I'd be probably really happy to play against them.