Thanks for your input. We're going in a different direction.

As for that poll on what color of fiber cement we should use for the siding (Barn Red or Charcoal Gray), um, never mind. The reds we looked weren't going to work well with concrete, and the combination of charcoal gray, concrete, glass and window frames couldn't come together, no matter what we tried. Plus, the charcoal gray that looked halfway decent was getting real dark, and we were in danger of this place being called "The Black House." I'm not particularly concerned about resale, but this is nuts. Maybe next time, expensive Swiss imported siding...

So, we're moving to the more conventional, safer one-step-short-of-cliché cedar, but not the cedar shakes you're familiar with. This will be what some people call "channel siding", where the boards are long and thin, and not beveled, but are ship-lapped and offset so that there's a narrow (half inch?) channel in between boards. Probably horizontal.

To keep this from becoming rustic (shudder), we'll use select, no-knot cedar and galvanized aluminum trim elements to make sure it's really clean. Everybody, including Barry the Builder (Bob wasn't available), seems to be happier and somewhat relieved. I'll budget for periodic maintenance.