The Gaelic/Celtic Union is an idea that has been batted around for a while now. It might be political fantasy, but the populaces seem to be general amenable (not including, ironically, the various "unionists").
Honestly, the Brexit that would probably keep the most people happy is if England and Wales minus London left the UK, and the remainder of the UK plus London stayed in the EU. Scotland would have to become a special economic zone though.
I wouldn't. Mainly because being the latter half of a country name would be a slap in the face and a general embarrassment of the nation. All for just over half the population that for some reason didn't want money from the EU because most people here are that poor. Amazing really.
Haven't you got that backwards? It would be the rest of England leaving, against London's wishes, while there's nothing but inaction on London's part. How have you got that turned around so that it's London forcing their will on the rest of England?