BEags
The vast majority of staff at the vast majority of bases are 8-ish to 5-ish, so why not? Those sqns/sections on base that did not fit into this "majority" would then be able to fulfil their commitments at times to suit them. The FJ/RW crews (and just a few of the ME types) should find the thought of being captured and having their nuts put through a mangle sufficient motivation to keep fit (with respect, a large ME accident would have few survivors...?).
Even when I joined a mere 14 years ago, complulsory PT would have been anathema to us RAF types, but I think that even in that short time the fitness levels of entrees into the RAF have been slipping iaw the proliferation of modern games consoles and the anti-competitive nature of sport in schools. Add to that the fact that there is less opportunity for those already serving to take part in recreational sporting activities due to operational pressures and we end up as a fat and wheezy service. On joint operations, I have been staggered by the marked difference in attitude towards exercise taken by the Army and the Navy compared to the RAF. In the RAF there still seems to be more people willing to sneer at a "jock-strapper" than someone who does not frequent the gym.
We are a nation of steadily increasing girth and that is reflected in the services. I have seen personnel unable to carry their deployment kit any distance due to being unfit and/or having a LMF. I am not a weights monkey, a muscle technician or a gym queen. I'm just a normal bloke (and not all that fit) who despairs at the state of some of the people that wear the same uniform as me and go to war with me. Being fat and unfit just isn't bloody military.