I think if you have oval bases you could use Ironjaw brutes with spears or, potentially, whatever weapons you wanted. To me the notion of a 'Big Stabba' is not only a big spear, but in my case, the big guy that does the stabbing himself! As long as it fits with the rest of your army's theme and is on the correct base, I can't see why most TOs wouldn't accept that as legit. I've taken mine to Realms at War here in the UK, and will be taking them to BOBO in May
Edit: This is pure speculation! No idea what TOs would say, but I'd wager cool converted Big Stabbaz would be fair game!