Deep side-bracket boxes will dominate your install.http://www.protectconnect.com/spinningProducts.html
These fellows ^^^ introduced the best thing going -- at the top of the market. Bad timing.
They would've been absolutely ideal for you.
They have now been quasi-cloned by the NEMA crowd. Read any recent copy of EC Magazine.
There are some nifty Romex-to-metal gadgets out there. I leave it to others who work Romex to rate them.
As for MWBCs -- they seem to be out of favor.
For such a large home I'd expect a hefty Service, 400A, and perhaps a sub-panel.
The latest trend in McMansions is towards star distribution -- of water, of data-com, and even of electric power.
It should be interesting.