In principle, I feel like the prospect of a European Union Test team would be a fantastic one - it would expand the Test cricket universe, provide challenging opposition for countries like Bangladesh and - dare I say it - Zimbabwe, and allow talented players from so-called "minor" countries a chance to shine.
However, the logistics involved would be insanely complex. Plus, I personally am of the belief that while Scotland and Ireland are competing as separate cricketing entities, Wales should be too; the creation of more "blocs" of countries that compete together in international cricket further blurs the line between domestic and international cricket, and makes the definition of what constitutes and international match and what doesn't extremely vague. Everyone's statistics change, suddenly certain players' eligibility changes in a heartbeat (would Ed Joyce still be available for recall to the England ODI team? Would Alexei Kervezee's Worcestershire contract, or that of any other European playing county cricket for that matter, need to be changed to accommodate him as an Overseas Player, now that he played for a Test-playing nation?), no-one knows who they play for any more.
It's a nice idea in theory, but in practice, I doubt it'll ever come anywhere close to fruition. The best we can hope for is for one or two of the European nations to have progressed somewhere close to Test standard within the next twenty years.