Here is the OP's idea of complexity, find a splat book which rests on an already broken game (base 3.5e) and break it some more while masturbating furiously to how good your build is and then come to complete ecstasy as you stack 20-30 buffs on you. Then ascend into Pun-Pun status. Great experience for the DM and everyone at the table.
3.5e was so good with all those false choices when it comes to min-maxing. Oh, yeah, not to mention that you're almost always suffering from feat tax. Gotta' pick up all the meta magic feats, gotta' pick up power attack, etc.
I mean I had fun, but no one in their right mind would say that the system had meaningful depth because as you soon as you begin to measure it there's already a god build that does everything better (and relies on splat books).
Simplicity is not a bad thing, e.g Chess, Go.
