I believe that there's not a lot available for guitar and voice in a "folk style" but with a quasi-classical feel. Richard Dyer-Bennett did a lot of these folk songs as art songs and his arrangements might be published somewhere.

Trad "folkies" would eschew this kind of thing but if it's well-done and skillfully written, I like them. Why not? Most folk songs that we hear were never intended to be accompanied by the guitar anyway. It's of recent origin so I think that if it's tastefully done, why not?

I like ol' Burl Ives accompaniments because he played tastefully and completely simple unadorned um-plunking to back his songs.

Josh White was a stylist who tastefully accompanied traditional blues and folk songs in a non-traditional way (his own).

Someone really should transcribe some of these great arrangements by the popularized folk performers such as White, and Dyer-Bennett.
Some guitarists during the 60's folk boom such as John Stauber,
Ray Bogoslav, Millard Lampell, Erik Darling, Freddie Hellerman did tasteful quasi-classical musical arrangments of folk songs. Pete Seeger and Peggy did some too.

Frank Hamilton