Really cannot see BA moving to T1!
Firstly, I cannot see them wishing to move to T1 as they would have to build a new lounge and if they want to bring Oneworld together then wouldn't it be easier to move to Terminal 3 or even T2. The only OW carrier at T1 is Finnair (Aer Lingus do op at T1).
MAN is in desperate need of a new Terminal before any more expansion.
If BA moved to T1 then Vueling, Iberia and co would also relocate..?
T2 is full in the mornings and empty in the evenings, perhaps with Iberia and Vueling having evening flights T2 may be a more suitable Terminal. There are no wide-body gates left at T1, Etihad and Thomas Cook have taken Pier B.
It may even be more suitable to move KLM and Air France back across to T2 to free up space for more BA at T3?
Another move could be to shift UA across to T1 so it is with the other Star carriers and would free up a little extra space in the early mornings.
They should:
1. Move KLM and AF to T2 so all of SkyTeam is together.
2. Move UA to Terminal 1
3. Keep BA at Terminal 3
Remember Stands 56, 57 & 58 will be able to be used without busses for S17 so that will free up two to three extra stands on T3.