I think many of the bad melee weapons could just have their downsides removed with no other changes made to them. Weapons with meaningless or bad upsides like the Sharpened Volcano Fragment and the Vita-saw could be made into technically straight upgrades from stock and it really would not matter, because no one is going to use them unless they want to use them, which is the same reason as anyone using any stock weapon other than the Bottle and the Knife. It would just make it so you aren't punished further from using them, as not using something actually semi-decent is enough of a downside. Some of the weapons' upsides are basically downsides in themselves too, actively being worse than stock in their main effect; just remove the part in red from the weapons, they don't need that.