BA are very strong to the US, and MAN has a comparably strong offering direct to the US. The YoY shuttle figures for BA are the ones you need with VS removed. Part of the issue is BA DO want long haul passengers from MAN, in the same way KL, LH, SN, LX and TP do. They just have an appaling track record of making enough money in doing so, they don't get non LHR at all well, never did!
Certain people, with good reason are anti BA because they left the MAN point to point market as they were rubbish at it. However it's unlikely BA would pull MAN-LHR as their whole LHR model needs short haul feed.
Btw if you connect LHR T5 to T2, is that even a protected connection Oneworld to Star?