Am I alone in that I’d like to see some weapons that are used by NPCs be added to 47’s permanent inventory? Like the AR/HK416 based rifles (Fusil G1/G2), the non-suppressed ICA Raptor SMG, and such? It’d add more variety to the SMG and assault rifle categories, and besides, in like Hitman 2 Silent Assassin, once you discover a weapon it can become part of 47’s inventory.
I personally think that would be nice and such for more variety, especially since the item display cap has been increased.
There was one SMG that was used (I’m pretty sure) by some of the black uniformed guards in Mendoza that became an unlock. ETA: And let’s not forget the Hackl Sniper Rifle that’s in Chongqing…
But honestly, as nice as the extensive armament we already have is - there are really only a handful of weapons I (myself) only ever use. I can’t speak for anyone else…
So then it kinda becomes a ‘Trophy Hunt’ or gun hoarding simulator. 
Not to knock on your idea/request…
The only (or main) thing I’d hope for is not so much as more obtainable weapons as it is weapon customization. Which could probably be expanded upon after obtaining more/diverse weaponry.
If anything, I’d wait and see what Freelancer mode offers in this regard. It’s said that we’ll be able to lose weapons/gear if not retrieved (even suits). So I don’t see why we couldn’t take additional weapons from missions. 
The thing IMO that I think is slightly odd is that those items I mentioned are already in the game. So to me it’s a little odd that they’re not actual inventory items.
Then again, I do find the rifle and SMG sections a bit threadbare compared to the pistol and sniper rifle sections. I get that both are weapons fitting 47 and his missions, but I’d like a little more variety, though I don’t exactly want it to become World of Guns LOL.
I’d also like to see the ability to customize weapons, not just simple reskins. Maybe a mode or addition to the game similar to Sniper Assassin, but instead of having to unlock mastery or do challenges, you have to figure out not only what weapons suit you and your tactics/strategy, but attachments or ammo or such. Even go as far as customizable stocks, barrel/caliber swaps, etc.
That’d be a neat idea for those who are both gun experts and those who just want to experiment with different things. I don’t know if or how IO can implement it into Hitman 3 without a at least fairly significant game mod or such.
That being said, I’d like to see IO add at least one long rifle (not a bullpup) that’s suppressed or loud, and maybe a new semi-only self loader.
I mean, considering the dearth of new items that aren’t reskins, I don’t really get why you can’t unlock all NPC weapons. It’s at least marginally better than, I dunno, a reskinned syringe, plus they’re already there in the game.
I thought there might be some gameplay reason, like in hard mode in Hitman 1 people could spot differences between guns, but hey, bringing the right gun to disguise yourself as a guard is pretty much the only use these guns would have.