I accept Tourist's view that he can join straight up as aircrew but as he well knows (an he is being dis-ingenuous if he denies it) the AIB is not populated by the FAA but by Bubbleheads, Fisheads and Engineers.
Matters not. Before you reach the AIB you have to go to OASC to pass the aptitude tests and only then will you be boarded by the AIB. Assuming you have passed OASC tests then your boarding team at AIB will have an aircrew member.
Any Service flying is fantastic fun, but each offers a differing perspective. If you are dead set on FW then clearly the RAF is the way to go (but the FAA offers the FW route to the very best of its candidates - you have to be special because it is single seat FJ or nothing - there is even the possibility of training through the USMC rather than the RAF system). If you fancy flying in the most challenging environment (maritime and lots of foreign visits) then the FAA is for you. If it is an Apache and Afghanistan you hanker after then the AAC offers the excitement (but I recommend talking to an Apache pilot about his quality of life).
Best of luck.