I built an enclosure for my 1000mm x carve when I got it so will share my thoughts on it.
Full disclosure from the start though, I’ve barely used my machine, as shortly after getting it I took a liking to hand tools… and just starting to look back at it.
The enclosure makes things noticeably quieter which is nice. The enclosure keeps dust inside and not on everything else in the garage. The enclosure NEEDS good access to the machine to tighten and adjust parts. Even with this built in, it’s still a lot more of a PITA then it would be if it were open on a table. I like your fold back design for this, I think it would be easier then my doors. I have doors that swing sideways upfront, and the back is actually two separate pieces hinged at the top. I cut holes in the sides for access to the X axis ends.
I went with MDF for the torsion box and it’s been as flat as can be.
I made some changes to my design since I built it. I lowered the front drawer and added the keyboard tray above it, then side mounted a monitor on the top left on a swing out arm. You want to think about where your keyboard/mouse and monitor will be with your design. You want to be able to access and use them easily from in front of your machine. Trust me on that one, having things mounted on the side sucked.
The back non folding part of your enclosure should have some way to access the back parts on the Y rails. The little drawers on the left might obstruct easy access to the left side of the machine being so far forward.
Looks good though.