Tomorrow I will order the remaining panels that I will need to purchase: Drive bay rails, window blanks, and a 1/2" x 1/2" motherboard support rail for the rear panel.
I have decided not to shore up the internal vertical panels as the added support will not be needed (...I think... I can always go back and correct myself should it be necessary).
The next step is to cut the Left-panel fan hole, and to start the profiling of the edges that I have cut (where applicable), I hope to do this prior to the weekend.
The next hurdle is to think about mounting the PSU.
~ Is there a specific PSU frame that you had in mind? There are other options such as cutting the rear panel so that the PSU will mount directly to it. The mounting would not be load-bearing as the PSU could rest on a small raised pedestal.
The PSU cut-out would look similar to this:
The only issue with the idea is that I would need the exact measurements of the PSU that you intend to use. This also introduces another potential issue later on: Changing PSU's wherein the mounting is different.
Another option is to have a square opening that is over-sized. Although not as refined as the cut-put, it would provide the leeway for any PSU, and would still remain in the spirit of an "open-air test bench".
P.S. I hope your Family is healthy and happy.