Why not adopt the same allowance system as the civvy FTO/FTEs get (or used to when I was doing it)? The deal was £8.60 per hour or part of hour flown (used to make for a lot of 2hr 05min sorties as I recall............).
Personally I can't see why we (I currently have aircrew in my team) have to fork out for a "flying allowance" when they are sitting behind a desk.
Of course, we could always get rid of the daft system that effectively "charges" budget holders for the bods in their teams, in which case I couldn't give a t*ss about flying pay........... :-)>