Hear me out: make anti-champion mods armor mods instead of weapon mods. You could put them on elemental affinity armor that corresponds to weapon type (solar for smg an ar, void for scout and hand cannon, etc.) and whatever smg, ar or what-have-you you have equipped gets the perk. That way we could use exotics we like. Maybe some exotics would end up OP, but we'd at least got to use our favorite exotics in nightfalls. Some of those guns were hard for a 2nd tier player like me to get and it sucks that they mainly sit in my vault.