Funny how democracy, one person one vote and the like is the be all and the end all until it becomes inconvenient.
You are confused about the nature of democracy. It does not allow people to vote in other countries' elections.
For instance, I, as an American, do not get to vote in Canadian and Mexican elections.
If, after the Palestinians have all been gathered up and bussed to the Gaza Strip where they belong, they wish to set up a democracy there, that will be perfectly fine.
But Gazans will never be allowed to vote in Israeli elections. Israel is a separate and independent country.