Point taken, but in regards to the original B1900 question:
Being a FAR-23 Commuter certificed aircraft, we can conclude that without a published Vmcg (only Vmc), V1 can never be set lower than 1.05 x Vmcg, and subsequently Vr never lower than V1.
Hence, no reduced V1 for the B1900 no matter how low the braking action might get?
Isn't that what the original question aimed to adress?