My idea of a foul weather bike for mixed terrain would have 40c or wider all terrain tires, fenders, belt drive, 7-speed or more IGH and flat or somewhat upright bars. Something that can be hosed off without fussing over the chain. And tires with tread that can be brushed off fairly quickly with a scrub brush and water to get rid of the mud. Chevron tread patterns seem like a reasonable compromise between grip and easy cleaning.