This isn't about Protestant Caucuses, it is about self-defined caucuses based only on an individual posters beliefs. If you want a Protestant Caucus you already have one.
However, I'm willing to bet that there isn't even consensus among the Protestants on what Sola Scriptura means or any codified standard for what differentiates scripture from Scripture. Absent any authority like a Magisterium it means whatever each individual believes it to mean so it is only arbitrarily enforceable and certainly not defensible.
Actually we heard some Catholic whining about the term Protestant caucus..
Without addressing whether belief SYSTEMS were intended to be covered by caucus definitions, is it really hard to know who belongs to a “Sola Scriptura” caucus?
Just as a “Catholic Caucus” is open to anybody who holds a personal belief that they are Catholic (until such time as a sizable number of other Catholics complain that the person doesn’t sound Catholic), a “Sola Scriptura Caucus” would be for people who think they believe in the doctrine of “Sola Scriptura”.
Those who don’t understand it probably don’t believe it, and wouldn’t participate. Those who think they believe it, but don’t really, might soon enough be apprised of this by other participants.
Meanwhile, the body of believers who believes in SS would be allowed to discuss all manner of doctrinal issues, knowing that their arguments will be based on differing interpretations of scripture within the SS framework, without having to be distracted by arguments from tradition, reason, or other extra-biblical texts.
Just as the church caucuses not only allow discussion of church matters, but also more general matters from the narrow perspective of a common belief.
It is a requirement of a “caucus” thread that it not disparage any other faith of belief. So what harm could there be to other faiths that a thread be limited to a type of belief?
Any topic that you are interested in, can be posted to an open thread. The rule of “duplication” has never been applied that I can tell to an open thread version of a caucus thread.