I think stat modifiers for races are a great idea. I think classes needing huge values in a particular stat to be viable is what poops up the entire thing. Look, the problem is people are asking themselves "Why play a human fighter when I can play a half-orc? The stats are so much better." If Strength wasn't so
required for fighters (or intelligence for wizards, wisdom for clerics, etc) such as by taking away the ability modifier to attack rolls or save DCs or what have you then it wouldn't matter so gosh darned much that the Half Orc has +2 Strength. You might even start thinking "Half Orc wizard sounds fun" without the standard "hurr hurr it so funny becuz half orcs r dum" because the intelligence penalty is no longer absolutely prohibitive.