Well, that one guy had a really cool lore friendly idea with the Dwemer technology rifle.
Lore reasons aside... There's the issue of an AK-47 feeling like... An AK-47 not in just looks but in the feel of using them. I believe magical staffs have been brought into Skyrim though I never used one that does damage yet. Reloading, perhaps some type of recoil those would be issues, I'm not sure if it could ever mechanically feel the same as in Fallout for instance. Personally I'd like it if they brought back crossbows which were in Morrowind, a scope on the crossbow is about as far as I could feel to be lore friendly. Dwemer crossbow with a scope, that on the other hand would feel just right to me. Way easier to make than an AK-47, and arguably quite lore friendly at least by TES standards in general.
I've never played CoD...what gives? And your copy of Skyrim will STAY without guns. No worries! From what I understand, mods are not contagious viruses.
Personally I have no interest in guns in Skyrim even lore aside, I find the mechanics working well to be highly questionable. That all aside... Yeah mods aren't contagious. If someone wants to make a completely lore contradicting mod that for instance... Made dragons breathe out clouds instead of fire, made cliff racers replace dragons, turned altmer into the shortest race, turned steel into light armor, made nords resistant to fire, dumner resistant to frost, bretons vulnerable to magicka, bosmer more hated by animals, made a single 1 hander (non dual wielding) do more damage than 2 handers, made shields block less damage, made destruction spells that healed, made flame atronachs cast frost spells... Okay you probably see where I'm getting at. Yes it would be blasphemous to TES lore, and yes I wouldn't want things THAT contrary to the lore in MY PERSONAL Skyrim, mods are NOT contagious. If someone for some reason wants flame atronachs that cast frost spells, I don't feel the need to ridicule them for it. If I was forced to get their mod it would be different.