One of my thoughts when I saw your sketch was that hatcheries use incubators that can hold maybe 60,000 eggs stacked like that. These are the commercial hatcheries that may hatch 1,000,000 chicks a week. Late in incubation their heat problem is not keeping them warm but to keep them from cooking themselves. The embryos generate heat late in incubation, heat can build up. They also need good air exchange since the eggs breathe in oxygen and out carbon dioxide through the porous shell. They use fans to keep the heat from building up too high and for air exchange. You are not going to have anywhere near that number so I don't know if you have to worry about either of those or not.
I think you will need access to all of it. Part of cleaning will be finding and removing chicks that die, not just poop and soiled bedding. You will want to be able to see if chicks are acting sick. I'm not sure how well you can do that with the trays in the middle. I imagine you want to stack it for floor space. If it were me I'd look for alternatives but if that were the choice I'd want the layers spread out as much as reasonable.
I have not raised Cornish X and don't have any magic numbers as far as room. Can you run a test? If it were me and building it out of wood I'd try a 4' x 8' section to take advantage of standard wood dimensions. Same size as my raised bed gardens so you can reach everywhere from the side. My initial run would be 50 chicks in that since you are only going for two weeks. That should tell you what you need to know about space. But remember, I'm just guessing. I haven't raised Cornish X.
Since you are in the US (thanks for providing that info) I'd call you county extension office and see if they can help. If you get lucky and they have a good agent they might hook you up with an expert, probably at your state land grant university. Or contact the Ag Department of your state land grant university directly. Whether you are starting a business or just doing this to provide meat for yourself this is kind of why the Extension Service and land grant universities were developed.