The aim assist would do more work for you than the acog would. For the sake of argument, you could just take off the acog and engage at mid range, you still get farther aim assist than the smg does, but it's not as far, so the window for comparison would be smaller. I'd try to find a better example that really isolates just the aim assist as a factor, but it's been a long time since MW2 and many of the iron sights escape me. Red dot on both I suppose.
I get that you don't like aim assist, but if a game has aim assist, having an option to turn it off would make you much worse than your competition past close range. You can say the aim assist would make you worse, but it wouldn't. I really wouldn't be opposed to an option to turn it off, it would make those who want the option happier and make my enemy easier to kill, so win win.