If I had to pick one thing that is most important when dealing with roleplaying games, it is this: Balance.
Balance is everything. Balance is the reason for the system. Additionally, this should be inherent in the system, not something that you add later on. It is not OK because you can change the rules, just like my car is not OK without an engine just because I know how to build an engine. I’m not going to just shrug my shoulders when the dealer hands me an engine-less car.
Every system suffers from this.
D&D: Not all feats are equal.
Able learner (everything is a class skill) is clearly superior to various feats which make 2 or 3 things a class skill.
Menacing Demeanor (+4 intimidate) clearly superior to Skill Focus(Intimidate) (+3 to intimidate).
Warhammer suffers from this.
Flee! gives you +1 movement, for D10 rounds, under special circumstances.
Fleet footed gives you the same, for infinite rounds, any circumstances.
They cost the same. They aren’t worth the same. Sure, fixes can be applied (Lets make it +D10 movement for 1 round. The total is the same, but the advantage is the headstart you get, which is exactly what flee should be).
However all this is doing is building the engine for the car you bought. Do I like to homebrew? Of course! Do I like to customize? Absolutely, but I’m changing my automobile (because I want to) to this: