Well, I guess I didn't mean a solid 4x4 field so much as "enough terrain to fill" which would mean plenty of hallways connecting rooms, etc. Not necessarily laid out in density the way you have it displayed above.

I mean, I'd watch with great interest if you did, but I get it. That is a lot. I started a vault/bunker/underground lair build a couple years ago and completely stalled on it. I built three rooms and a hallway. The process was tedious, for sure, so I am keeping my eyes open for any new inspirations.