George,
I say you need the neutral per 300.3 (B). Should there be a severe imbalance in the load, and no neutral to counteract the magnetic fields, there could be a considerable heating problem without a neutral. The 24” nipple rule is a gift but I’m sure the code panel felt that 300.3 (B) would be abided by when they wrote it. To take up to 30 circuits through a nipple and not use all the conductors of the circuit seems to be pushing it. Just my AHJ 2 cents worth.
Tony
