I’ve done a system like this, but instead of points remaining ships that have been wounded lose points proportionally per mast lost.
So for example, if if the Raven’s Neck lost two masts in the game, it would be considered to be worth 6 points. It’s a 12 point ship, and has 4 masts, so each mast would be “worth” 3 points.
For ships where you can’t divide the cost up evenly by mast, round it and the last mast is worth extra. So for El Acorazado 21/5=~4. The first 4 masts lost loses you 4 points each. The last mast is worth 5.