| Imagine an older, seasoned guitarist with a great jazz background, and what he/she can bring to your ensemble? I think the reason you're having such a hard time finding guitarists is because the percentage of them that learned "formally" (i.e. along with music theory and such) is very small.
And you aren't planning to have an improvisational ensemble? Or are you limiting improvisations to 8 or 16 bars in the middle and then everyone sticks to the sheet music?
Most Jazz fake books that I've seen really only have "lead sheets" anyway - the melody line and chord changes above. IIRC, my Jazz Piano course (books) really taught how to turn a chart into actual music (i.e. how to play the left hand in various styles and how to interweave the chord changes and melody lines) - and most of the charts in the lesson books contained chords such as: I IV V IIx, etc. and didn't even have a key signature (which makes it instantly transposable to any key).
And as an aside, the music I've heard in Cowboy Bebob (so far) is blues based - all I-IV-V changes. (OK the theme music does have that chromatic bridge in it) | 
