So, one of the things I want to do if I ever get a chance to have a house wired to my specifications is have each room have its own lighting homerun to the panel, but multiplex these homeruns onto a smaller set of lighting circuits at the panel in a star bus topology instead of the "daisy chain" of lighting circuits run all over current houses. This makes the wiring of the house itself clearer and easier to follow logically speaking, while allowing multiplexing schemes that keep large, contiguous areas in the house from being darkened by a single breaker trip.
While 312.8 permits splices in the panel by ordinary (wire-nut or push-in connector) means provided the panel gutters do not exceed 40% wire fill and 75% overall fill, the use of twist-on or push-in connectors free-floating in the panel seems to be a somewhat...sloppy way to do this. A perhaps more neat and workmanlike approach to the problem is offered by the use of UL 1953 listed power distribution blocks, which are commonly used to provide enclosure-mounted splicing and distribution points in industrial control panels.
While the products in question, when appropriately specified for wire size, are clearly suitable for the application at hand (a block rated for 175A continuous is not going to pose a problem on a 20A residential circuit), I know of no case where they've been deployed into a panelboard cabinet to provide cabinet-mounted splice or distribution points in a neat fashion. Is this a Code-legal thing to do, provided gutter fill does not exceed 312.8 requirements? Is 312.8 even applicable to splicing points that are affixed to the cabinet (vs. floating in gutter space)? Would modifying a stock panelboard cabinet assembly in this way void the UL listing or violate some other portion of the NEC?