I'll add another argument. It is usually assumed that organizations tend to defend their existence once created. At the moment, we have a set of european institutions that are defending themselves quite well: European Commission, European Parliament, European Council... Nearly all of them are of an economically conservative culture.

If such a system would be created, this means that some European "social" administration would be created and then defend itself, but which culture would be representative of traditionnal European social state rather than of anglo-economics. This would participate in a useful balance of power at the top.

A free fox in a free henhouse!