Are you limiting your options to 9mm/5.56 only, or are you open to other calibers?
If you're open to others, the 300Blackout is one of the better cartridges that can use both supersonic and subsonic ammunition reliably for suppressed/unsuppressed use. Knights Armament makes an excellent removable suppressor. But if you want to keep the total length to 16-inches you will have to pin the suppressor to the barrel. Otherwise you'd have to go NFA with the short barrel if you want the removal suppressor also.