HitpointType::Mana will not exist, everything will have String alike IDs, so you do not need to include other peoples APIs if you just wanna flag something as “does damage to generic magical energy” or DamageTo(21, “Mana”, insertBodyPartHere)
You are thinking WAY too constrained to everything having unchangeable Classes, instead its pure Events and Numbers, and the Mods decide to react to those Mathematical Events.