The problem with Israel being the one state, sovereign over all of what used to be Palestine, is that the Muslim Arabs would simply out breed them and in time, the Jews would be a minority in Israel. Look at Lebanon. It was supposed to be a majority Christian-Arab country and it was for many years, but when the Muslims finally became the majority Lebanon proceeded to destroy itself. It used to be ‘the Switzerland of the Middle East’. Now look at it.
Between immigration and reproduction, Jews are catching up in population growth. Arabs remain narrowly ahead due to increased life expectancy. Lebanon does bear looking at. The Muslims became the majority after the PLO relocated there from Jordan, when the Hashemites kicked them out for attempting a coup. Christians have been leaving ever since, because they are being driven out. Same thing is happening in Bethlehem in Israel.
No plural marriages is a solution.