Additional animations for fighting weapons and guns

[Funukemaguro]

While it would be fun to add guns and devise a way to match the gun reload motion currently provided by the existing vanilla, some guns are fundamentally difficult to implement, such as bullpup style rifles and double pistols.
So I wanted to add a new animation: .......
I can sort of see how this could be accomplished by replacing the existing AnimatorController with a new AnimatorController that adds transitions and states and assigns a new WeaponHoldType, but I'm not sure what script to use to do that. I would appreciate it if someone could tell me how to do this.

Also, this method has the disadvantage that if others want to add animations, they will compete with us.
So does anyone have a better idea?