The FSP is a selection process/tool not a training device.
Previous flying experience (PFE) is used to determine which level of FSP you complete. Do NOT limit yourself by fantasy PFE limits in order to control which level of FSP you complete. Fly if you are passionate and can afford to. If you cannot fly then know LOTS about aircraft, particulalrly the aircraft type you want to fly. The key here is to show the assessors that you are as keen as mustard for the job. There are many ways of showing this and PFE is just one of those ways.
There would probably be nothing more frustrating for a board officer than interviewing a candidate who knows nothing about the job and is not passionate about the role.
The need for fast jet pilots is probably increasing all the time and the need for multi engined pilots is probably limited by excesses in the system. READ- RAAF probably highly focussed on fast jet selection, though there will always be some requirement to recruit and train pilots for ME aircraft.
However, the FSP and PSA are not RAAF centric and a career in either of the other services is guaranteed to provide a challenging and very rewarding career opportunity so don't get hung up on RAAF. Look around at what the other services can offer.
Passion and a determined and focussed application is key. If you're not in this category then you should look at other careers. It is competitive. It is challenging and it will be exciting and it can be disappointing. Just like the real job!
Remember the 6 P's. Prior Preparation Prevents