I completely agree on having deep player character options while still keeping things as simple as possible for GMs. From a GM perspective, I love the way some rules-lite games (my preference is for the OSR/NSR style) make it so easy to run a game in that system. But my players, and me when I am a player, aren't very interested in the bare-bones player character options that those systems usually have.
In the system I'm creating, player characters have a skill-point system that they can use to build out their character by purchasing the equivalent of feats to build whatever sort of character they like. It is straightforward, but can get really complex for those players who like to explore those systems.
Meanwhile, NPCs can be represented with 2 stats (Hit Dice and Will Dice), which can be used for HP, morale, skill checks, and saving throws. For combat encounters, you only need to add an attack, and for social encounters or significant NPCs, you can add personality traits and motivations, to facilitate GMing the NPC.
The goal of the system is to marry the player character mechanical diversity that you see in systems like Pathfinder or GURPS with the ease of GMing that you see in the OSR. There's also a sort of "playbook" equivalent which give starting character builds for those players who are more interested in the roleplaying than mechanics, and just want to take something and run with it.