for a commuter, you're going to want clearance for 38s or 32s with fenders, rack and fender braze-ons, probably a 73-74 HTA, and a 4-5cm BB drop so people can run the cranks they need to for their size. size it "long" instead of "tall" for more fit variety.

for what it's worth, the BMW gangster isn't that middle-of-the road; they designed it as a durable frame that would barspin a 700c. i'd call it closer to the trick riding end of the spectrum.