If sticking with the classic controls causes me to get my butt kicked because I can't freely move the aiming reticle. I'll learn a new control scheme if that's what I want to do. Still not a reason to force me to use use a particular control scheme.
It sounds like the issue is the auto-aim with the 3rd person mode - not that it would cause you to get your butt kicked. I would guess the 3rd person modes rely on auto-aim quite heavily.
Personally, I'm wholly against multiple control styles (not button layouts) for MP. Having both controllers and keyboard/mouse is not fun. It forces people to use keyboard/mouse. I thought allowing both MOVE controls and controllers was a bad idea for Resistance 3. I'm all for forcing players to use a specific input device or control style for MP.
That being said, it would be nice if the game allowed a "classic" 3rd person scheme option for the SP game, even if the default controls match the lock-strafe mode used in MP.
I'm used to lock-strafe and used it as soon as it became available. I wouldn't be that annoyed if it wasn't an option. But, both schemes should be an option in SP.