I might expand the list of corals. The idea is to make it an LPS, softie, and mushroom tank. Maybe downgrade the size if all the criteria get met with smaller size.
Wow! You took an 8 year break from the thread!
Do you have a system running?
I have a 270 gallon Miracles tank (72x36 footprint, I want to say 27 tall) on a maple stand that I got used for $1,200. I have an Apex, 2 Radions, 2 Reefbrite XHO's, 4 Tunze wave pumps, a Lifereef skimmer, 2 Sicce ADV 10.0 pumps (for return and skimmer pumps), a Bashsea sump, Bashsea media reactor, and an Avast kalk stirrer. I know I'm underlit, but my halides were too much heat for my house and I had the Radions. I really lucked out on the tank price, and most of the equipment came from my previous tank. You could probably do it for $10k with a used tank, some patient classifieds searching, and not needing custom cabinetry or floor reinforcement. I was fortunate that the only place I can fit the tank is almost entirely over my foundation, so I used a couple jackposts in my basement for stability.
Conversely, you could be looking at several tens of thousands of dollars if you want a new tank, paying for movers, home reinforcement, or if you need to have your house opened up to fit the tank. It's sort of like asking how much a midsize car costs. Are you talking Hyundai, Toyota, or Maserati?
My tank would handle most of what you have listed, but I believe the naso needs something a bit bigger. I'm under the impression that they need a lot of space or they start to show aggression as they mature. I'm not sure about desjardini requirements. I have a sailfin tang, which is somewhat similar in appearance, and it's been doing well in my tank for 15 months. I have 3 scopas tangs in mine, another zebrasoma species, and they bicker a bit. 5 Z. flavascens would probably do okay for a while, but aggression is likely to increase as they mature. I originally wanted them as well, but they became essentially unavailable for a while.
The Genesis company went under. I'm not aware of any dedicated water change systems out there, but peristaltic pump setups have become pretty popular and are fairly inexpensive. You'd just be putting some pretty good wear on them since they're better for low volume dosing.
I would look into the Neptune Apex and Coralvue Hydros for your control requirements. They both have pros and cons and have occasional issues, but either one is capable of monitoring and controlling your system.