Hate the Aeron, but I'm a big guy. I don't really like mesh chairs. I happen to like Bodybilt
Back when I used to get this asked all the time it was
2)Good Monitor - back then, multi monitors was unknown, today I'd say monitors, and I'd say budget putting them on VESA arms
3)Good keyboard. I have a bunch of model Ms - the original IBM ones feel slightly better than the current Unicomps, even if made with the same molds/gear. Three of them are back at Unicomp right now getting cleaned/overhauled. How many companies will clean/restore a 25 year old keyboard (One has a Mfg date in 1992. another 1999, one early 2000s)
4)Good mouse, but these days, that is easy
Basically it comes down to ergonomics
Now as you are building a building, put that rack, and anything like it in it's own room/closet, and SOUNDPROOF it. You'll be shocked how much noise really effects things. It is part of the reason I build my own PCs, to put the quiet gear in, not necessarily the fastest. I don't need blazing video, a nice, relatively slow card that is silent is more important to me
I used to be an audiophile, so you would think I want super audio - nope, just background.
A quiet HVAC system if you are building your own building.
Good lighting. I've had bosses look at me strange when I show up with my own tracklight to setup what I like
Basically it is "Make your work space someplace you want to be"