The non elected clowns in Brussels aren't saying what their plans are for a EU army and big pension changes. They are going to be announced after the referendum. Might scare off the voters in the remain camp. The British army for 1 won't serve in a EU force. They would rather resign. Anyway we are the US's cats paw unpaid and unthanked and working for them.
Sounds like you've been reading The Express, or something? Many countries wouldn't, which is why it won't happen. As they say, so openly, they have no fundamental objection to sending more troops to join UN forces as and when they're needed, but the prospect of an "EU army" might even dissolve the EU completely (as something surely has to, eventually, in its present form), which is why there's no real suggestion of it other than in the more hysterical media.
For a start, quite apart from all the practical difficulties, and the fact that so many countries object in principle even to it being discussed, it would undermine NATO.