Couldn't agree more. The vast majority of the crew at LHR couldn't care less about what was happening down at LGW.
As for mixed flying, most airlines are ACTUALLY doing it successfully! EK, EY, KL, LH, QR, SK, SQ to mention a few of them. One of the reasons why Mid-fleet wasn't much of a success was probably for having far too many fleets at one time; LGW EF, LGW WW, LHR EF, LHR WW and LHR MF!
They see it's working at LGW and they probably feel it can be done at LHR. After all, they are not running a charity.
I'm at WW and have decided not to say yes or no to Project Columbus until it has been presented. Most of the crew are extremely negative towards this but bare in mind NOTHING has been announced and therefore nobody can actually say what the "package" will be like. Perhaps it would be beneficial money-wise, especially for the ones on the new contract since 1997, which also of the majority at LHR are on.