And if we need the realism argument (though really, with how guns work in this game talking about realism is a bad joke), firearm proficiency carries well across all types in sizes, as principles of shooting are very universal. There is also matter of familiarity but that's true for all weapons.
Personally I would like to see Rifles/shotguns stay a distinct skill and have more to offer than the use of standard pistol ammunition for most models.
You would pretty much need to fold every weapon into two master skills (melee, firearms) to make them balanced in access and flexibility and power.
I'd also make a case for combining Electro-Tech and Secure-Tech into just Electronics, but my feelings aren't as strong on that one. Again, I'd just make secure tech devices a higher level check since they require more advanced calibration and installation than a TV or a toaster oven. I readily admit this could be lack of advanced game knowledge on my part, but I can't imagine the archetype that's interested in a field relating to those skills and doesn't take both simultaneously.
That no one was skillsofting their skills would not probably be great comfort to the one who came off worse in that situation.
Having separate skills at least somewhat implies a content parity between them, maybe not perfectly but it's pretty rough in a game with almost no documentation and permanent skill assignments that some skills have massively more content than others.