Short answer: It’ll end in tears.
Long answer:
I’ve used bb7s for 10years, and if I were you I’d not try a floating rotor. The rotor needs to be able to flex when applying the brake because only one pad moves inward (unlike with hydros, such as juciys, which have 2 pistons moving simultaneously). A rotor with an aluminum carrier does not offer the flex needed to function properly without damage to the carrier; the aluminum would not return to its original shape in the same way as steel after it flexes. This would give the illusion of the rivets coming loose, when in fact the carrier has become deformed.
Hope that’s not too rambly…and hope that helps as well.