1. every s-mode has the same OP worth 25 (when hullmode is cheaper then rest of OP is added as to thee ship budget)
2. max OP worth s-moded hullmode is 25 (more expensive hulmode canot be s-moded; plain general rule)
(OP prices are for capital size, smaller ship sizes has smaller limits accordingly)
Some interesting ideas there. It could be tried. Generally I get the feeling this change is trying to compensate for problems that are already very small. Since SS is a singleplayer game, there is always the luxury of just leaving it be and not having everything be the exact same power level as everything else. This may "feel wrong" but overbalancing tends to result in weird appendixes (as in, the bodypart) to existing systems.
I'll offer an option #3: Every story point added to a ship just increases the ship's OP by 10/15/20 whatever is the correct number for its size. That's it. No more S-Mods. With the same SP limits as before. Could also pay a single SP to add a bonus effect to one of the ship's hullmods.