Dragon Magazine #310 lists a bunch of specialist versions of the fighter class. It sounds like it treats them as different classes that just have a lot in common with fighters, but it also says they "are to the fighter what specialist wizards are to the wizard core class".
As far as I’m aware, a wizard that specializes in a school of magic has no general restrictions placed on its ACF/feat choices–only specific ones for certain feats and features (an evoker can’t take an ACF for conjurers, for example)
So, what about specialist fighters? Could a pugilist take the Overpowering Attack feature from PHB II, or gain ToB’s Martial Stance feat as a bonus feat?