Ah. Sorry about posts. I was referring to a post by Ithirahad
here about having a block that not only controls turrets but also other weapons types. Anyway, I don't think that having a fixed hard cap on the number of controllable turrets is a good idea. It only encourages huge turrets. Same thing with having it be controlled via hotbar slot. With your limit, it becomes "make 10 huge turrets, so I only need one person to control them."
I think the real restriction should come from not being to target things behind you while in remote-turret mode. If you're sitting in a chair or computer, then you can't look behind you to shoot at whatever's there. You can aim your firepower better in one direction, but you can't use it in another direction.