I think UEFA might be more open to leagues amalgamating now as long as they remain under UEFA's auspices. If the Scots, Dutch, Belgians, Swedes, Danes, Norwegians, Austrians, Portuguese, Serbs, Bosnians and Croats all came together and said we want to change our domestic league set ups it would be difficult for UEFA to ignore a block that size. UEFA got a fright when the Super League thing was launched and they've made concessions to the big clubs and big leagues now to keep them onside.
I can't see why UEFA would object to a Scandinavian League being created, for example, that still had promotion and relegation from the various countries involved. The creation of 'new' domestic leagues that might challenge the dominance of the EPL and La Liga might actually be welcomed by UEFA. The various domestic associations would need to be in full agreement too, that might be an issue.