i'm knocking out a few of my early naive implementations and it feels awesome.
my structure is now
all of this is edited in the Unity inspector now thanks to ScriptableObject, and although having Weapon handle behavior is still a little awkward, i think the full customization of the system will start to shine when i layer a Projectile class onto Hitbox and can make weapons do some truly interesting things.
i also realized that C# delegates were always a thing and i didn't have to go looking for UnityEvent to do that for me. but they have some minor differences that are useful to know! for my sake, the restrictions of C# delegates are actually safer so i'll probably switch to them whenever i think of it.