I've been doing a lot of research on this online and reading through old threads on here. Here are the plans I know so far:
Poured concrete walls, floor, and ceiling in the basement
Roughly 12'x15' in size
Lip of door to be raised about 6" from basement floor to minimize risk of water coming in

Questions:
Construction- concrete PSI and thickness and gauge of rebar? I've seen 4,000PSI at 8" and #7 rebar
Electric- need outlets and lighting. Best brought in by small conduit in the wall I would imagine. Anywhere in particular?
Water- no plumbing to be brought into room for risk of water damage. Still contemplating a floor drain but will be difficult since where we're building is relatively flat.
Humidity- controlled with dehumidifier. Can use safe inside the safe room if need be. Also thinking about doing radiant flooring.
Ventilation- I'm partially convinced I don't need to worry about it this but could me mistaken
Vault door- I would like an inswing door that is capable of of being locked from the inside. I've looked at a few manufacturers and Brown seems to be leading so far for me.
Exit- I've been contemplating a small hatch door in the ceiling but not sold on it just yet. It's another point of weakness, water, etc. but having another way out just in case is tempting.
Any information would be greatly appreciated. Thank you!

I've never seen a basement without a floor drain. Personally, I would want one in the room to drain dehumidifier into. If not, at the very least run some conduit through the wall that you can drain the water through to a large container, so you won't be dumping it as often.

Plan for the future, leave enough room in conduit for data cables for video recording system.

@a1abdj Surely you would have some good input