As seen above. Prolong the control to sometime in the early 50's.
1. No Balfour Declaration would be a start.
2. No division of Palestine into two (preferably with 1920 borders), and allow Faisal to be Emir of Palestine. Maybe even setting up a Westminster-style parliamentary democracy, adapted to Palestinian conditions.
3. Get the Ashkenazim and the Palestinians (here including the Christians, Muslims, Druze, and Sephardim) on the same side, working together. Difficult but possible.
4. Enact major land reform so that everyone has some form of property/real estate and actually hae a clear economic programme for Palestine, including granting Imperial preference to Palestinian goods.
All those would be a good start, IMO.