For the record, while the Sewing Machine may be/is installed on ships, it's not really any good at targeting planes and the Cannalans don't attack your ships with helicopters regularly (or planes for that matter). Although, maybe I should tell the Cannalans their Buccaneer boats are getting trashed and they can't rely on them for torpedo delivery any more, that's probably gone on too long anyway.
But, that's a separate discussion. Anyway don't worry, I'll mention SAMs on boats so calm down y'all.
For a rule of thumb in general, your ships currently have a miscellany of weapons stuck in the spare deck space (autocannons mostly) and replacing those with something else that fits and isn't too expensive is usually fine.
As for the SPAAS Garlic, it doesn't strictly introduce much new technology, what you're mostly trying to do is hook an existing missile guidance system up to a gun that can be rotated and elevated by electric motors already. Not actually that hard but there's a risk of it being [complex] like the missile it's based on, you're still copying the IR system by rote with the first chemical compound you could figure out to do the job. Packing the radar into a salamander might be a challenge (it normally takes up a truck) worthy of a revision on its own though, so that would be quite difficult but you could still try.
That said I'll give the vote a little more time, since some people do want the speedbump. I just wanted to step in and say the Garlic isn't totally against the rules or anything.