There's a false equivalency between Mustachianism and minimalism. You can certainly be both. But you can also be an incredibly wasteful minimalist, or a very frugal maximalist.
On the Mustachian front, your job would be to make the home as efficient as possible. #1 is energy efficiency -- what's the insulation like? Is it 2 x 4 or 2 x 6 construction? Are the windows low-e, and does the home have good sealing to minimize heat loss? What about solar or geothermal? Presuming that you're stuck with whatever you bought, can you add things like thermal shades or better caulking to improve performance? What about a natural landscape with minimal water demand?
But then there's lifestyle efficiency. You want appliances that you use daily, instead of countertops and cabinets full of things you use once a year. One comfy chair is much more useful than four uncomfortable ones. You want sufficient storage and ready access for kid toys, family games, and all those other activities you want to be able to do -- maybe even a dedicated craft or hobby space if there's something one of you enjoys. You want storage for the lawnmower and bikes and sports gear, again in a way that makes it readily accessible. You want long-lasting floors that you don't need to change every 5 years because of either dirt or fasion. And of course you want a workbench in the garage or basement so you can do all those DIY projects to avoid outsourcing. ;-)
Our house is bigger than we need, for sure, especially with one kid now off at college. But I love it, and it's worth the money to me. It is old and has the kind of character you don't see nowadays, and my DH is slowly re-doing all of the rooms (in the dining room, he has already done a cherry built-in and cherry coffered ceiling, and we will shortly have cherry trim -- the room just almost glows). The house was a summer home and so has been a total energy hog in winter, so we have done insulation and windows and everything else we can think of to reduce usage (including buying into one of the state-sponsored "get your power from solar energy" plans to at least help offset our still-high power use). We had to move the kitchen and rebuild it completely, but I now have a kitchen that I designed myself for exactly how I cook, with solid cabinets, dovetailed drawers, heavy-duty slides, and an indestructible countertop; it still works and looks great almost 15 years later, and I wouldn't change a thing. And the best part is that we are in a first-ring suburb, where my kids can walk and bike wherever they need to go, and DH and I are both within 10 miles/15-20 minutes of our jobs -- he's so close that he was able to buy a plug-in hybrid and almost never use any gas, and now that I'm working at home the only time I drive is to get to my acupuncturist.
I'd like to bullshit myself and justify it by saying that we could get a much bigger house for the same money if we went out another 15 minutes or so -- or a really huge house for a lot more money if we'd "upgraded" like many people we work with. But the reality is that we could also have bought a smaller house for less money if we'd wanted to, and we need to own that decision. I mean, failing to keep up with the Joneses, when the Joneses are buying 6500' mansions in the boonies, isn't exactly something to pat yourself on the back over, you know? So, yeah, my house is a total splurge. It also fits us completely, and I don't regret the extra money it has cost us.
