Enter the Surly Troll. 26" wheel bike, with means to attach anything you want (within reason)- disc brakes, full line guides, post mount brakes, derailleurs, racks (front and rear), fenders, specially threaded holes to attach their new trailer, and horizontal dropouts for single speeding.
Here's how I have mine built up (for now):
Single speed. Right now it's fixed. Front hydraulic brake. My favorite seat/saddle and handlebars. And giant tires. 26 x 2.4! I know they're excessive, and my choice is almost purely aesthetic. I just prefer the way they fill up the frame, especially on a mountain bike. If I was a car person, I would probably be this
So far I've enjoyed the ride. The heavy, heavy wheels/tires do take a little energy to wind up, but if I keep them up to max air pressure it's not so bad. Plus, I don't fear the potholes quite as much on the 2.4s. Which is important for my daily commute these days- have you seen S'ville Beacon Street? Pinch flat city.
I'm looking forward to taking it off road a little. And probably for a little light touring. And give it a geared drive train sometime. Or 3 speed. And maybe try it with some skinny tires. Or whatever other project I can come up with.