Not sure what your letter is supposed to illustrate ? Nowhere (as far as I can see) does it talk about crew complements. Nobody has suggested crew at LHR take a pay cut, oh except the BASSA loonies, and even for new fleet BA is still suggesting market rate +10%. So BASSA shud be negotiating LHR market rate +10%.
LGW crew had the nous (at the time) to see that they needed to adapt and change to survive in "their" market. Your TU are basing a lot of their argument (well depends on what day/what way the wind is blowing quite what their argument is) on H&S and crew numbers, which they deem not workable with new complements (as opposed to what appears to be the crux of the correspondence you posted - remuneration).
Then again BASSA change their tune so much.....imposition, 40% pay cut, 50% pay cut, H&S, imposition again, macho management, new fleet, LGW MOA, pilots deal, Willie Walsh, Jedward.....have actually lost track quite what they are arguing about/have balloted on ???!!!