Item attunement only works on mundane objects (SM, pg 54). Foci are magic items (SR4a, pg199).
What you do is get an external SmartGun and attune it, and have it attached to the Ruger that is the focus.
What you do is get an external SmartGun and attune it, and have it attached to the Ruger that is the focus.
Incorrect, read item attunemnt you must physically interact with/use the item attuned.
IE: you could item attune AR gloves for a hacking adept to give a bonus with working in AR (but not full VR).
Similarly smartgun is an electronic gizmo which talks electronically to the eyes/glasses. You're not interacting and manually using the smartgun ACCESSORY, you're doing it to the gun. Doesn't work.
You need to item attune the guns themselves.
I have nothing against turning a gun into a melee focus. But not a ranged one. I remember the reaction when I suggesting turning my defiance EX shocker into a weapon focus (it's 'shots' trail wire back to the gun so it's still technically in contact w/ my aura). Still it was a funny idea.