I'd love to see something like this. A style we here in the nordic region often refer to as "troubadour" is what I was primarily thinking of, if that gives you any idea, but I'll try elaborate:

At its core this is the "guy with guitar" concept, but with a much more defined bass than the currently existing Campfire styles have (hence the "Solo-Accompaniment" part). So I was oddly enough not thinking of jazzy styles here, but more along the lines of "Are you lonesome tonight" or "Love me tender". I'm struggling a bit with coming up with case examples for Ev feel that you might know, but this sample might give you some idea.
The vital element is the well defined single-note bass, followed by rhythm (strum or pick): https://youtu.be/FlDcpNFRudI?t=2m

I'm not sure if I'm explaining myself all that well here, hope the sample helps, listen to the bass notes!

PS. This should be a set, with a range of tempos and feel, waltzes included. Here's a sample of just that, by the same guy (a real master of this art form):
https://youtu.be/OfOZA-i82bo?t=1m3s