

Cutting off your arm isn’t necessarily illegal (didn’t look into that specifically, and it may well be), but from my quick googling is, legally required to be reported by most if not all medical professionals. That report will almost certainly fall well within the rules of what will put you into a 72 hour involuntarily psychiatric hold.
So… Cutting your own arm off, regardless of legality, is likely to lead 72 or more hours of imprisonment.
I don’t know where exactly the line between cutting your own arm off for fun vs. to study it vs. self treating with homemade cancer drugs falls on the danger to self and others scale. My line would likely be a lot closer to ‘do what you want to do’ than most judges, but I do think cutting off your arm for most any reason is a reasonable bar for some outside inquiry, from a mental health standpoint.
Just noodling here as well.
Depending on the level of quality you’re looking for, that could be a very doable project, or a mistake, only you can find that out! Based on your questions, I’d have some reservations about tackling that.
My specific thoughts: Figure out if it’s custom to that wall forever, or has any possibility of being used elsewhere in whole or in part. building it in chunks that attach together is a good idea regardless, for ease of build/if anything needs to be changed later.
Those are some pretty wide shelves up top, and you’ll definitely want to consider how much weight they’ll potentially hold, and if they should be very thick or have additional support in the center.
Hiring someone to do all of it, or just a bit of design/consulting isn’t a bad call depending on your skills and quality desired.
The other suggestions of find some furniture (IKEA or other) that checks enough boxes with some minor add-ons/modification is a good option as well.