And in the the US, there's no such thing as a "frozen ATP." You have to have 1500 hours to take the written test.
First question would be where do you want to work? Different countries have different certificates (it's not really a license in the US.) So if you want to fly if the US, you need a US FAA certificate. If you want to fly in Europe, you're going to need to have a JAA (or whatever their name is this week) license. And of course if you want to work in the US, you're going to need the right to work in the US, if you want to work in Europe, you'll need European rights.