Go for it, I reckon, otherwise you'll never know.
If you stick to your guns, it shows determination, as long as you're not negative about the other options.
If I had to interview someone who was saying 'Well, I'm going to do my damndest to be a RAAF pilot, but if for some reason that can't happen, I'd still really like to fly military aircraft, so give me a shot', I'd think, fair enough and good luck.
Of course there may well be reasons why they can't, or don't want to take various people in different circumstances, but if you're up front, positive and motivated, I don't think you can go wrong.
Both services have their own cultures, to coin a buzzword, but in the end you're flying good machines (mostly) and getting good training.