AviK
I’m sure many would be happy to become citizens of and move to rich European countries or the USA (as would many Israelis or citizens of just about any country in the Middle East or Africa for that matter.) You would need to get these countries to take them. Good luck with that. It’s just not practical and frankly those other countries have no reason to take them. The Palestinians had been living in the land that is now Israel for hundreds of years. Like I said earlier imagine if a bunch of Native Americans put together an army came into New York, (their ancestral homeland) took over, and insisted that all the current residents of New York leave and move back to the countries their grandparents or great grandparents came from so they can re establish a Native American state.
Signing a loyalty oath wouldn’t solve the demographic problem. If the state is democratic the Palestinians would be able to vote away the Jewish character of the state. Signing a loyalty oath wouldn’t help for that.