Remember Expertise as well. Extra damage per non-critical bullet is a major part of the SMG appeal, especially the silenced (low base damage) variant. You already have Sprint, wich is good as you need to be rather close, sometimes point blank, to hit well. Lastly, consider Opportunist+Suppressive Fire, as the latter provide a slow-effect, the combonation making your bursts do permanent 15% more damage. SMGs are really strong, though if you are doing only light crafting, perhaps get mechanics to 50 or so, and chemistry to 20, to make repair kits (weapons degrade rather fast with) and more importantly armor-piercing bullets, to overcome your main problem with mechanical threshold/resistance.
For SMG i would also consider taking Suppressive Fire + Opportunist. Suppressive fire gives debuffs for everyone in the cone of fire, and that debuff will proc Opportunist damage increase.
In regard to the crafting I am unsure on how high Mechanics, Electronics and Tailoring need to be for sufficient stealth gear so the numbers maybe be not optimal.
