Pardon my ignorance, but which domestic or Irish airports does BA LGW 'hub' with, either directly or by codeshares? Last Oct I went MAN-LGW-NAP and it was excellent. But I believe the MAN-LGW flights have now been reduced.
Oh, definitely no doubt over the LGW ops, I think for a domestic transfer it's easier than going to LHR from experience. I tend to use LGW when going to PRN which is a MAN>LGW>PRN leg and the timings are well matched.
Routes wise from LGW, using the untrusted source of Wiki:
Edinburgh, Glasgow Intl, Jersey, and Manchester. That lack of domestic routes makes it rather apparent that LGW isn't designed as a hub airport for BA.