Being that my tank is about 15X smaller than yours I had problems when I built my tank wall and found out that it was too small. Since it sounds like space is abundant for you here is what I would do if I could.
1. If I could do it over I would of given myself more top tank clearance. I only left myself 8" and should have had about 14" - 18". Now I have to squeeze new lighting in there.
2. Also since I don't have a sump my Protein skimmer barely fit and needed adjusted. I would definitely build a compartment below just for the sump area and even a chemicals and tools area. A utility sink would be very accessible. Don't forget about a Quarantine tank!
3. I didn't expect to make much mess with water, but during changes and maintenance I spilt water onto the base which is painted drywall. I should of designed a more waterproof area or some type of drainage system.
4. I would of made more arrangements for better power supply. I would of installed a seperate breaker just for my tank wiring. Only because I have 3 tanks on this wall.
5. We made everything structurally sound using wood for my tanks. If I were you I would look into something more stable and not likely to settle or move. Probably some form with concrete blocks, boarded, formed and then finished. Maybe even a slab. Not sure. That's alot of weight. Definitly would consult with a trusted and experienced LFS
6. If there is going to be a wall above I might design some kind of recessed compartment just for my lighting. I would make it fire proof safe and accomodate some cooling fans in there to and give myself some access from the back and top.
Good luck, Sounds like an awesome project. You can never waste time doing research!