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?
I was actually correcting myself; I was surprised to find that Vmcg seems to be omitted from the Part 25 regs (although not from practice, generally) as far as publishing a number.
I'd say that the absence of a published Vmcg means that V1 can never be set lower than 1.05*
VMC, assuming that Raytheon/Beech never established a Vmcg per 23.149(f) and so the option in 23.51(c)(1) isn't available.
However, it's possible that they DID establish a Vmcg, and that they have set V1 based upon that Vmcg, but have not published it in the manual per a strict/pedantic reading of 23.1513 (similar logic as the part 25 pedantry I described). What it means in that case is that the operator doesn't have any data which would permit setting a lower V1, since they don't know if they are VMC or Vmcg driven. But, in the absence of any guidance in the flight manual, you'd have no performance data for a reduced V1 anyway, so would be operating outside the 'book' with regard to e.g. distances. It's the "applicant" who selects V1, not the operator.