Right now I've a good steel tall Panasonic road frame I've made into a low gear single speed (fast start, easy dirt trail, great on the street) bike. Straight, low, and narrow Richey handle bars. I love it, the simplicity, frame geometry and lightweight. Sort of an urban 'café racer'. It's just great to ditch the derailleurs and cables.
Trouble is, it's road tires and not good for mud and grass.
I'd also like disc brakes and 26" wide tires (won't fit my wheels).
No shocks wanted, I'm old school. Shocks just add weight.
So...who makes such a thing (inexpensively)?