Smart rounds... I dunno about the balance there. When you buy a mod from an independent, is it per-unit or do you get the prototypes to start churning them out en masse? Because obsoleting a major game mechanic by giving your Vanguard grunts the ability to ignore most cover seems pretty brutal. But if it doesn't scale to mass production and is a thing you give your elite sniper hero... still pretty nice, but not a game changer, especially if other round options make it an opportunity cost.
Later game mod, seeing as it costs 50 influence to acquire, which is apparently quite a bit of influence.
And we don't see how much cosmite it costs.
And it is restricted to firearms weapons only, so really of benefit to Vanguard, and to a lesser degree assembly and Dvar, because their Infantry is short ranged single attack firearm, whereas Vanguard are medium range repeating.
Assembly do have a firearms based sniper though, so that could be a cool mod for them.
Also, afaik, mods purchased work like mods researched, in that they are available for all eligible units.
Thinking about the T4 units, the only one that is firearm based is the Earth Crusher I think, and imho if you have one of those, the smart rounds are just icing on the cake :