Good luck, but if you're looking for quick answers with dates to a very complex question of politics and policy, you may be disappointed. I don't think you can really do any more than you are doing just now - shoot for your dreams, and don't accept a job doing anything else with the promise of a cross-over in branches later. It's certainly a possibility, and plenty of people have done it, but could take years and you might miss your opportunity due to other service commitments. You sound like you've got a few years yet before your time runs out - volunteer at big airshows? Join the RAF Reserves?