Israel in 1918 has been addressed before, so I'm going to focus on the wrinkle: monarchy.
Who's the king in this case? Is it just George? That might be almost acceptable to the mostly Socialist, anti-tsarist Zionists. Anyone claiming to be King of the Zionists, though, is going to have basically zero legitimacy. If the British insisted, you might see some unenthusiastic acceptance in the short term, but even the Fifth Aliyah (of Jews fleeing Nazis, who are more politically diverse and less likely to complain) were mostly socially liberal and probably opposed to monarchy on ideological grounds.