First off I’d like to say that I’m not too enthused about any particular implementation suggested, just that I would like to see the ability to modify melee weapons more than “add nails to a board/bat”.
Metagaming is not obligatory, you don’t have to try to be amazing at everything possible, I can go months in game without even using a melee weapon, why would a highly effective modified weapon be obligatory?
Even modifying your guns isn’t obligatory (A basic SMG is highly effective with a little skill and ammo), neither is building a fortress, or crafting your own stuff, or becoming a cyborg/mutant, even using vehicles isn’t necessary.
You can live almost forever using a handful of bear traps, a longbow, and hand made tools.
Why have CBMs, or gun mods, or crafting, or construction? Obviously they’re just more things for people to learn, and a hindrance for people who don’t know how to properly utilize them.
I don’t ask why?, I ask why not?
(PS: “This is a waste of developer time” is a pretty good reason")