Always pro controls and I bowl much the same as you, set a field and try and bowl to it with variations in length and seam angle/aftertouch, only changing the field periodically or if I'm trying to do something specific with a bowler.
Like the right saddo I am, I'll look before any match and jot down my bowlers strengths. If he's predominantly an inswing bowler I'll bowl largely inswing, if he's strong on bouncers/yorkers I'll bowl back of a length and mix it up between those. I definitely try to bowl differently with each bowler. I do often wonder if some of what I'm doing makes any difference at all, for example I'll only move aftertouch direction mid run up and generally not very much, in my head that makes more of a difference than swinging it round from 12 to 6 o'clock before you've started running. It probably doesn't make a jot of difference right enough but I'll keep doing it.
