It's also worth noting that Rogues have a number of disadvantages (low hitpoints, low saves, no armour) that the increase in skill points is meant to offset.Every class has its plusses and minuses.
Besides the fact that these skills are pretty deeply entrenched in creature build and balance considerations and things like that, their individual function is also hard coded into the game engine for a variety of things, and that's beyond our ability to adjust.
I was thinking more of a mod that make it when you put points into spot, listen, and search it counts for all three. So not making new skills just modifying it so the skill point in one skill count for all three. And for characters that have points these skills could get the point in the other skills back.