Does anybody have any idea if a Polish insurance company will insure me to drive this vehicle in Europe (outside Europe becomes a different matter entirely)? Or would they refuse insure a non-Pol outside of Poland?
If it's registered in Poland, it's probably a non-issue. As long as you can give a Polish address to them, I really can't imagine it would be much of an issue. The fact that you'll be listed as a co-owner should simplify things even more.
(Incidentally, Polish insurance works on the principle of the car being insured, not the individual. The individual still has to be named that posesses the insurance policy - but any other driver can happily drive the car without an issue. For instance, say you have a friend here who has accidentally got himself wasted in a pub. You can turn up and drive him home, entirely legally)