I think it's an excellent proposal and I'm all for it. No borders, no custom officers, no visas. On 20.256 sq. km of land I am sure some 18 mio people could squeeze additionaly.
Bluester - You wouldn't be all for it if it happened. Even the most forward thinking individuals can't help getting pissed off when they're being sidelined in their own country. In some schools in Britain Christmas services can no longer be held in case it offends other religious groups!!
The joke is that most normal moderate people in the 'other religious groups' are more than happy for Christianity to be celebrated. Stepping on a national identity and central religion just leads to bigotry and hate. Can you imagine France, Germany or America being restricted in the way that they celebrate Christianity?