I think the big trick here is to find a good BBQ sauce that is lower in carbs. Its tough, but it can be done. You probably wont be able to find much under 10 carbs a serving, but remember a little sauce can go a long way. About half a table spoon of sauce should be enough for one tortilla. So if you play your cards right, all the ingredients together could equate to about 9+ carbs for a small pizza. Its really up to how sweet you want it.
If your really feeling ambitious you could make your own low carb BBQ sauce. More on that one later though.