Let's say that Flying Pay was (A + B)F, where A+B = 120% and F is the current rate. If you allow everyone Rate A (say 90%) and Rate B is available in dribs and drabs for additional qualifications (QFI BI, A2 and A1 increment, IRE increment, QWI increment, EWO, Auth, Air test....etc etc) up to 30%, arguably you would reward those who provide the most value.
BUT:
1. Would you take them back to 0.9F when posted, on a ground tour etc?
2. Could you trust JPA not to ar$e the whole thing up?
When I left, my pay was about half what my civil counterpart would have received for doing the same peacetime tasks, let alone anything for OOA.