If I had only 1 bike it would be a build based on my Black Mountain Cycles Monstercross frame thats currently set up as a touring/commuting bike, or it would be based on my current Fairlight Secan gravel frame.
The Fairlight Secan has road geometry for frame angles, bb drop, and fork trail, it has mounts for fenders and a rear rack, and can fit 700x47mm tires.
I could happily use it as a paved road bike, gravel bike, commuter, touring bike, and twisty river bottom singletrack.
The gearing on it would work as is for road, gravel, and commuting, but I would want to change tires if it were used more for paved road. And gearing would need to change if it were used for loaded touring, but that wouldnt to switch a few times a year for the trips.
stock pic from company-
pic of mine from solo gravel ride last fall-
