I must respectfully disagree about your statement on which slot they take; if they're a special, they must compete with the other very nice choices we have there. However, I will agree that they would replace greatswords entirely (who's going to take full plate and GW or HW when they can have full plate, HW, and SHIELD? A minority, that's who).
I think it's important we clarify if they're being taken as special or core, because this could affect a lot of people's stance on it, mine in particular. Rare is out of the question, just silly.
I'll vote under the assumption it would be a core choice.