If the house is being built and wired new, wouldn't the most practical solution be to just provide a few dedicated 15A 240V branch circuits to 6-15 receptacles where needed?
The only code issue then would be what those 240V receptacles are intended to supply, but if we're just talking about one per room at most, couldn't they be for (mumbles next part) individual space heaters? As stated above, nobody has any control over what anybody actually plugs into them afterward.
