Fundimentally there are two issues:
Role of skill-using classes
1. Rogues are the only class that get 8 skill points; there are lots of other classes (Rangers for instance) that also have high skill points and a lot of must have skills. Are you going to move all their skill points down? If the answer is no then why are you picking on the rogue? If the answer is yes…. Do you really think that Bards & Rangers should have 4 skill points?
What’s the point of making them one skill if you charge twice? Why bother changing combining them at all?
If you lower skill points a rogue who takes skill points in these new skills is basically just as well off as if you hadn’t changed anything. One who doesn’t (or doesn’t take max ranks) is just losing skill points to your arbitrary house rule.
What about the monster races… are you going to gimp all the monsters who have spot, listen, hide and ms as class skills? Isn’t that a lot of work?
2. Power level
Rogues, I would argue, are already a frustrating class to play. The few places where they tend to dominate are either social games with very good players or people who’ve figured out some way to trick out Sneak attack with dual weapon fighting or weird magic items (permanent improved invisibility etc).
Most of their powers like sneak attack, and skill roles are DM controlled (the DM picks the monsters and the locations effectively deciding when you can sneak attack) or hidden (i.e. the roles occur in secret against stats the Players never see like enemy creatures spot checks).
Since you can easily adjust the monsters and the environment to make a rogue more or less effective I’m not sure that that having the –chance- of getting what are effectively two extra skill points per level (if they take spot and listen at max ranks) really is such a drastic bump in power level that they need to lose 25% of their skill points…
Personally if I were a player in your game I’d probably just say “lets keep the rules as they are and not waste time re-writing everything”.
