Both varieties of Smartgun require Armourer to install. And are you seriously attempting to argue that the internal smartgun doesn't take up any space?
..(Arsenal pg 148) ...the difference between the two of them( Accessories and modifications) is that accessories can be installed without requiring extensive mechanical
skill, while modifications requiring extensive mechanical knowledge.. ( (accessory)external version use mount and need armorer skill, no mention of (accessory)internal version however)
..by RAW accessories takes no slots, and Smartgun system, internal is listed among firearms accessories..
Modifications use slots, Accessories use mounts (while Smartgun system,internal (Firearms Accessorie version) do not use up , being internal)