The current items modifiers are decided simply by random and sometimes the modifier does not suit the weapon. It would be nice to have a "forge" (a building) where you can take your weapon and change a selected modifier for some money (price varying on which modifier).
For example, you got a bow with 4-star poison. You get to the forge and replace by a 4-star penetration instead for, e.g., 200k. Legendary modifiers could cost more like 400k-500k. I think this improves the weapon system at the cost of saving your coins to get the modifier you really wanted instead of opening dozens of chests, which is sometimes boring and disappointing.