UPDATE!
Work on the project is proceeding. After another attempt at a fort that I had to abandon, I have made great progress in the settlement of Bristlelance. The building that will house the vault is almost done. It consists of seven stories, two below ground, all made of pure ryholite. The first floor wall consists of rhylolite with lead sandwiched between it, I found a Galena deposit. Thanks for that suggestion.
Construction of the bedrooms and the dining room is complete, with all cabinets, chests, chairs, and tables made of solid iron, courtesy of the goblins who insist on trying to ambush me even though I have wrestlers who can punch them across half of the fucking map. I also have a magma forge/smelter complex (no sand on the map, regretfully), and an obsidian making room that doubles as a captive incinerator, but neither of those are part of the vault. The good news is that plans for the magma self destruct mechanism are back in. I have constructed the dwarfonuclear reactor according to Foe's blueprints, and should be ready to test it soon. I only used the centermost part of the design, but that should provide me with several thousand power. The river should soon be accessed to provide a limitless supply of water. I plan to use iron grates to keep any unwelcome wildlife out of course. Nearly thirty iron grates.
I still haven't worked out exactly how to make the workshops. I had some, but they didn't look as aesthetically pleasing as I wanted, so I'll have to figure that out. I'm thinking of putting them in the corners of the room and using the rest of the space for specialized stockpiles.
Work on the fluid logic for the vault doors is underway. The construction of the vault doors themselves has been delayed to to a steel shortage, but I should be able to trade for that.