Problem is that while aiming allows fine movement like you say, in a battle situation, aiming slightly off your target just so you can finely navigate over those boards over the BOTTOMLESS PIT (or whatever) is less than ideal.
FPSes usually don't have bottomless pits though... :)
Where you look you shoot. If you want a 'separate move/look' system, tank-style, you do need to have complete movement commands on the d-pad or WASD, not just forward/backward/strafe...
I just beat Shadow of the Colossus. In the 20 or so years of gaming I've been doing, SotC is certainly ranked in my top 10. I'd urge anyone who has a Playstation 2 and a love for adventure games to go out and buy it, they don't get much better. Review coming sometime this weekend...
This man speaks the truth!