Well standard racks don't really tell anything about how power distribution is handled. So why not make the OCP rack an extension of the EIA 19" rack? As it is, it's slightly wider, and as you mention the OU is slightly different from the EIA RU height. That would have enabled vendors to use the same sheet metal boxes, and MB dimensions etc. etc. for standard 19" gear and OCP gear. Or if you're going to be different, at least make it sufficiently different to be worthwhile. Is a 19-21" rack with ~RU/OU sized shelves really the optimal, or can we do something completely different that would be better (for some definition of better)?