With regards to regional links and thus the whole purpose of hub: forget it. As I have said before, the 'do nothing' policy of the UK govts across the last 30 years have ensured that all the regions have been snapped up by KLM/AF, Lufthansa + other Euro carriers (inc FR) and, now, all the ME carriers are taking pax from the regions to THEIR hubs.
Whilst the Conservatives love to shout about letting the market work - here they have signally failed by preventing the market and, now, the market has gone elsewhere. LHR is doomed to remain the smallest and most insignificant of European hubs. Game Over (Brexit or not)