Well The Netherlands is headed to a big fat no vote, and I think Italy is tired of France. This idea is so yesterday. There is a duty free zone, and it will remain. That was what the core was about. It had no other useful purpose.
I don't disagree with you at all; I was just specifying what would be envisioned as the so-called "core Europe".. The main impediment here is that this nebulous "core Europe" project has not stated purpose, and that's of course what your pointing out as well. They keep talking about this "core Europe" that will "forge ahead" or whatever. Forge ahead to what?? Such platitudes are all fine and good but the devil will be in the practical details. If all they want is to issue a mission statement, then they will have no problem. If what they intend to do is develop a supranational institution then that requires a detailed compact. A compact to do what? Aha! That's the part they've left out.....
As for the Netherlands, their problem is Muslim immigration. It's worth noting that their referendum is merely advisory (non-binding) and could easily be ignored if France voted Oui. The only reason the Netherlands is an issue is because France is going to vote down the constitution. If France ratified, then the Dutch No would merely result in the collapse of the government, and then the new government would either resubmit to a new referendum (which is actually quite a novelty for the Dutch - this is their first referendum ever) or they would more likely use their election that put them into power to legitimate ratification by parliamentary vote.
Please ignore my vexing grammar seizure! =)