Also consider the base-model Kona Jake. It still runs genuine DT spokes, Tiagra brifters, and double-walled rims (working from memory here).

As far as locking it: can you leave your super-duty, all-day lock at work so you don't have to carry it, and use a medium-duty lock for running around on errands?

I was given an old Trek 311 frameset, early '80s, built for 27" wheels. It turns out to handle 700C wheels just fine, using "standard-reach" 47-57mm brake calipers. With a rear rack, a pannier or rack bag, light systems, narrow fenders, and 700 x 25 tires, it's turning in average speeds that aren't far off my modern Paramount road-racer. Kind of a "sleeper..." 22 pounds with just fenders, about 26 pounds out the door with the works. If your old tank fits you well, maybe a 700C conversion...?