Yeah, lets just hope its not that much of an advantage. Because with CoD scoped SMGs have insanely quick ADS.
Putting an ACOG on a SMG doesn't make much sense, though, because more zoom means you recognise the recoil more.
I don't think red dot sights should affect draw speed, they're just an ergonomic preference after all, some people are better with irons and some with dots.
A sight ads slightly more weight to the gun and gives you an advantage when ADS. So there should be a disadvantage to it. And making draw-speed slower is certainly a good solution.
After all you can counter this with the gun-sling, if you don't need a Grip or Grenade Launcher.