I think Skills & Powers did something like that, as well as some setting books (e.g. Red Steel/Savage Coast).Going back and looking at the kits, I'd forgotten how many of the books had overlaps. There was a patrician kit for pretty much all of the classes, swashbuckler kits (with some differences) for warriors and rogues. Almost need to do a complete book of kits to consolidate date some of them. There may have been some small differences such as weapon proficiencies for wizards and warriors, but otherwise the benefits and penalties could have been the same.
Of course, some kits from the Complete books as well as various setting books did more than others in modifying the underlying class, sometimes to the extent that the result was really a new subclass (many of the kits from Jakandor were of this variety). But with Skills & Powers, you could in theory already do that within the class itself, so all the kits in it were fairly mundane (along the lines of 5e backgrounds).
I also recall that some of the kits were kind of dumb. The main one that comes to mind is the Amazon warrior kit, whose main ability is sucker-punching people who don't expect that a woman can fight. But the rest of the game is pretty clear that AD&D doesn't have gender discrimination, and women are just as eminently capable of fightering as men are.