Honestly, having a multitude of weapons in the game really isn't a great improvement. Unless you have clearly better versions, like a magnum vs desert vulture in the game now, they just take up space. Players will pick whatever weapon does the most damage (combined with ammo capacity) given the ammo type. If you have a few different kinds of 9mm guns and your chance of finding them is roughly equal and they have similar ammo capacity and damage, then what is the point other than just to have a different looking weapon? If they have different stats, then you are adding in a new set of tiers for the weapon type and there is a limit of how far you can go with that. Right now, they seem to try to limit tiers for a given weapon type... Stone, iron, steel for melee... pipe pistol, pistol, SMG for 9mm... etc. There are a larger variety of rifles, but how many people use most of them? If you use rifles, you tend to skip most and just use a couple specific ones (early game and mid/late game choices).
If you add more weapons, people will still just gravitate to whatever offers the most damage combined with best ammo capacity for the ammo type they want to use and ignore the rest unless you are not allowed to get a specific type until a certain game stage (like desert vulture or SMG not normally being found until later). And adding new ammo calibers just adds more inventory you have to deal with for no real value.
Melee weapons are where you actually have a good reason to add more weapons because there is a variety of ways to make certain weapons unique and the looks of them can be very different. With guns, they may look different, but usually not too significantly and they all do the same thing... shoot. With melee, you can have effects like knock down, stun, stagger, bleed, etc. that are different depending on the weapon type. Sure, you can add these to guns, but why have two different 9mm guns do different effects?
This is just my opinion, but more guns aren't needed. I would be fine with adding a few more melee weapons, though. But they would need something unique compared to existing weapons to make them worth adding beyond just different looks. I like swords and wouldn't mind then in the game, but in the end, a sword and a machete are going to be so close to the same thing that it doesn't really matter. And a katana versus "sword" (not sure what type you are suggesting considering a katana is also a sword) doesn't really give any real difference other than looks. Because weapons have quality levels, you can't just say that one sword weapon has slightly more damage than another and call it good. That isn't enough to justify multiple types of what is, in the end, the same thing with a different look. But adding in something more unique, like a throwing star or a staff that can offer different effects from other weapons can be nice to see added. As far as guns, I can see adding a dart gun with a couple of types of ammo maybe, but not more guns that do the same thing as what we already have.
