Hello Bill in Dayton,
Have you tried or concidered forming a "band" around your OMB act? For example, if a client wants a four piece you could add maybe two horn players and another vocalist. I'm not too familar with the level of musicianshp in Dayton, but here in Dallas I can find great players that can come in "cold" and sound fantastic backing me up.
I give potencial clients prices for a solo,dou,trio, quartet, and quintet. Since I mostly do Latin music I like to have a percussionist (mostly congas, and bongos) and then a sax/flute, trumpet, trombone, vibes, guitar... Adding a bassist, and drummer is a bit tricky though...
The guys I call can read and improvise really well and know when to lay out.
I like this way of working because I can offer various opptions for clients.
Best of luck, I'm sure you will do great!