That should work okay.

The only possible issue I can see, is that pulling one lever pulls both cables at the pinch bolt, possibly pushing the other housing out far enough to pop out of its hole and get caught on top when the lever's released, perhaps leaving the brake somewhat applied.

To mitigate this, you could attempt to somehow fix all the housing ends in place so the short length of exposed cable above the brake either bends or forces the unused lever to move (assuming full-length housing), drill deeper cable stops (allowing the unused housing to move up without coming out) in a bigger chunk of aluminium, or engineer some kind of fancy straddle-hanger with floating cable clamps.

That's if it turns out to be an issue.