This could be like when you craft your weapon you could have how ever many points to make a "upgrade" on your tool/weapon so like ex. attack,defense,enchantments. Idk its probably been said all ready but i didn't see it.
I'm not sure if I've seen a thread on it already either, but I do expect that we may already see something like this in-game. An early description of what they're working toward included a comparison to Borderlands, so I'm really hoping not only to have that sort of variation in weapons, but modifiers and upgrades for them as well. I don't know that there would be enchantments, per se, but perhaps a scientific equivalent that might effect ammo type, firing range, and all that.
I'm not sure if this applies to weapons, but Rho said that items will have levels between 1-100 or tier 1-10, and you can't upgrade that level(you have to find/create/buy better ones). I'm sure you will be able to upgrade in terms of bullets and "attachments" though.
Points to make upgrades?/ I personally like having to bring it to a blacksmith, and handing over crafting material and a small sum of money, it's more challenging imo.
I read somewhere that money was going to be a large aspect of the game, so maybe you can use money to upgrade weapons and armour and stuff?
I don't think that having XP would be a very good way to upgrade your weapons. It may start to feel like a chore to get your weapons upgraded when you need x amount of XP to upgrade them, so you need to grind for a while to get the necessary pints. Finding attachments in dungeons or from killing enemies or paying someone to upgrade them for you seems like a good option though.