The question is begged... Why?? Why keep a surplus? There is no cost benefit if the surplus is to remain, so why do it? In a couple of years we will be going down this path again when the final 744 goes.
I expect the word to Flt Ops from the top would have been - "for this year, you have to reduce your effective headcount by X and reduce your budget by Y". Simple as that, and that's exactly what they have done. Remaining surplus or no surplus is irrelevant, they met the target.
Next year expect the same - headcount by X, budget by Y, nothing more, nothing less.
No point in exceeding the target, it would just make it harder the next year.
Management 101 - the Qantas way!