I agree 100% with Tweaked's ideas. Super flexible lighting is key.
The 6 foot tank & stand will be sleek & modern, with minimal visual distractions.
I would also do an ATS from the start. Also an Apex controller with dosing pumps, ATO & high end controllable pumps for customized flow patterns. I'll plan out & implement everything I can to handle emergencies like power outages & temperature events. I might want a dedicated refugium optimized for copepod production (this is more about supporting mandarins).
I would also carefully map out a plan for aquascapimg with rock. I want the best aesthetics I can get combined with plenty of real estate to mount a lot of different corals. I think I have enough practical experience now to know how to create the best areas for acans, chalices, favias, hammers etc plus some SPS right off the bat.
Hopefully I can do it in such a way as I can plan for the growth of large impressive colonies that are spaced in a way that color combinations are optimized & stinging is minimized. The design would also feature plenty of sand bed (which my current tank doesn't have) since I found I really like scolys, tune anenomies, plates & other bottom dwellers. In other words I intend to proceed with a mostly long term finished picture in my mind. I've even considered modeling my ideas somehow on a computer or maybe even in clay, paper mâché or something like that. I'm probably going to have to buy some hand picked pieces, some very large, or buy WYSIWYG pieces on line.