I can't see that this is possible or practical.
BA tried transferring routes around the M25 to LGW some years ago but ultimately it failed. LHR works because of the transfer possibilities which it offers. Aviation is a global business not a national one. This thread could quickly descend into LON vs BHX vs MAN. I would suggest that is pointless & irrelevant. If airlines cant fly from LHR with its transfer potential they will go to another hub which does offer those transfer options: i.e FRA/CDG.
Plus European passengers who wish to go to London wish to go to London!
Some direct UK traffic routes may develop from the regions but to try to move European routes away from LHR would be to kill the goose that lays Londons golden egg.
Not doing down the regions: I live & work in them but lets face facts - this is a non starter....