Well, well, well.
I wouldn't replicate good posts, that complex and cleaver AI and simulation aren't good for roguelike and developer should concentrate on "how it looks for player" theme, but I write about my own experience, maybe it would be helpful!
Idea - player identical to monster sounds cool and great, but when it comes to real game play, that shining idea starts to fade.
You can trust me, person who managed to create one of dullest roguelikes in the world.
PC was identical to NPC and has is_player flag only, but you know, fighting equal opponents all the time isn't interesting (I don't mean stat identical, but identical checks to be wounded, killd, etc)! Damn, it is devastatingly dull!
Of course, it is cool, from time to time to have arena-like battle with equal opponent, but most of the time, player wants FUN!
So, game should give fun at first place.
Equal opportunities for monsters? What? Is it Monsters Rights League?
No!
Player wants interesting combats, so player wants to fight monsters, have challenge, win, have a chance to be fairly defeated and have epic feelings.
So, NPC should be modded to provide it.
PC enemies would be:
fodder, tons of them. They should have "easy to defeat injection".
they would give :YARRRR! ME STRONG, KILLED HORDES OF THEM!! ARRR!
Equals. Arena-like gameplay.
This is good challenge. Nice game experience, but NOT 100% of game play.
OverpoweredOr bosses. Epic fight, that player would win, because has "legitimated cheats" (healing, running away etc)
Epic battles, epic results.
Well. something like that.