It’s certainly a creative use of itemization, but it’s also incredibly unintuitive for that same reason (ex. gotta stack Vitality/Chaos damage instead of Pierce to boost flat damage).
In regards to spam Pierce casters, I’m not sure every damage type necessarily needs every archetype of character to exist.
I’ll have to think about the Pierce setup for this weapon, but I would not try to keep it supported if it means the primary function of the item has to suffer for it.