When we last had a discussion on this topic, I had the following idea:
A large shallow gutter, perhaps 1" thick, 2 feet tall, as wide as necessary. Spaced through the inside on perhaps 2" centers would be insulating stand-offs.
The kicker would be that every 'bay' (horizontal or vertical channel defined by the stand-off array) would be tested and _listed_ to carry a certain number of conductors _without derating_. You would have a large grid, and could run wires as needed to get from the breaker panel to the appropriate conduit, and as long as you kept to fewer than X conductors per bay, you would be in the clear. So rather than being limited to 30 conductors across the entire cross section, you might be limited to 20 conductors per bay, but have space for 240 conductors in the 8 horizontal bays.
I have not worked out the physics of how many runs would actually be reasonable in a 'bay'.
-Jon
