But Ireland, Malta and Cyprus can continue driving on the on the left? Would the province of Northern Ireland be given a special exemption? Seems fair given that it's already got half a foot in the EU already due to Boris's Brexit deal that sold them out and undermined British sovereignty with a line down through the Irish Sea. Or would you force a switch of sides when crossing the border? That would all seem to undermine the Good Friday Agreement though.
Two decades seems a bit arbritary, maybe even spiteful. Maybe an absolute majority of the electorate rather than just of those who bothered to vote or perhaps a clear margin of 20% or more would be a better measure of suitability to rejoin the EU. Anything less risks reversal a few years later.
I don't think many people supporting rejoining actually realise or support the idea that rejoining won't be on the same terms as before. You're alluding to that in a spiteful and unrealistic way, but your comment is based in reality.