Surely tz could/would simply define new Western, Central and Eastern European Standard Time zones and assign the relevant locations to them as from the transition date, rather than "model" them to existing zones? Or are you suggesting that systems that aren't properly updated would present misleading names to users?
WET, CET, EET, and related summer time zones have defined meanings, and are also used by other non-EU countries, who may continue to observe DST or not. It would make no sense to change names which are understood, to have different meanings, depending on whether a country had EU membership.
Ultimately, official and/or public usage will determine the names that are actually used -- and presumably the tz database will track that actual usage. IMO, if the EU decides to mandate that its member states must cease to observe summer time, and the EU or the member states further decide (as would seem quite likely) to keep using WET/CET/EET as time zone abbreviations then, given the importance of the EU within the wider European region, any non-EU countries using one of the current WET/CET/EET will have little choice but to align with the changes or find a new name for their time zone. -- John