Think sunk costs
You will need 10,000 points to book WM 13 months or to exchange to 2 Bedrooms in advance. Don't plan on getting 45 (RCI) or 60 Day 4000 Point exchange availability anywhere but the middle of the desert in the summer during a traditional school vacation season.
That being said 5,000 annual has a lower cost/point than 6,000 but they are hard to find, splitting costs $150 for the split and $150 for the combine or transfer making dividing impractical.
7,000 points have the same maintenance fees as 6000, you can always rent the extra 3000 you need for around $ 180 which is less than the maintenance fees of 3000 owned points - - - not counting the purchase price s savings of 1200 - 1500 on the extra 3000 points.
The little bit extra renting might cost over annual maintenance fees would take 15 to 20 years to recoup the investment, not including the fact that renting is optional, an annual contract is due until transferred out of your name.
The answer is 5,000 or 7,000