so your answer Frank is NO
no-one will guarantee regional connectivity from an enlarged LHR
Not neccessarily, it's so far down the road (if at all) no one knows the answer.
It appears to be on the radar and being considered by Parliamentarians and Heathrow Ltd.'s regional connectivity task force, and airports on the thinner routes (and their pax) appear to want it.
Balance of probability must be that there would be some arrangements made along these lines, but for now, it's all highly theoretical.
Clearly it
is a good idea and makes sense.