Unless you have a seriously good plan for the next 12 months, OASC are likely to be more impressed by you taking the decision of joining in the ranks now and it's likely you'll perform better at selection. Thereafter, NCAITC will be easier because it wouldn't just be on the bounce from ITC.
Lots to think about, and I'm sure the AFCO can talk to you about other trades [than driver] that could be of interest, but these days applying from within the ranks is just the same as that for a DE except you'll be better prepared; furthermore, commissioning clubs on most RAF Stns are an absolute gift.