Once we buy a house we think about this:
It's a safe room / shelter and it might just kill two birds with one stone.
And then:
I have a fear of safes large enough to be coerced into entering and then locked inside. I don't think they make safes with an internal escape mechanism.
The safe room shown has one problem. Its got an outward opening door. If used as a tornado shelter, debris from your blown up home can jam the door and trap you. To my way of thinking, all safe rooms should have inward opening doors.
The makers of safe doors will sell you an inward opening door with a release inside. Its really simple and can let you escape when the wind is gone.
Seven years ago my wife decided to build a new house. To get me to go along, she decided we could demolish the old shanty and build a new retirement cottage on the same site. When I realized it would allow me to build a vault room, I agreed. So I was talking to a friend and pretty excitedly told him I was going to build a 10x10 room. His first comment was "why so small?" OK, I bumped it up to 10x20. At almost no increase in cost, just the concrete.
But the rule of safes isn't negotiable. They're never big enough. Its not the size that causes problems, its the owner stuffing too much garbage into the space available. Boy, am I skilled at clutter and stacking. My current plan, one that isn't making any progress, is to use a glass TV stand I bought for $5 at a yard sale for shelves on an old executive desk. It will allow the display of gun boxes, some with guns in them, for the handguns. Then at an OGCA meet I bought a carrosel that will hold I think 18 long guns. Its new and has a terrible defect. There is nothing to hold the guns in the thing. The last thing I want is for my display to damage my guns. I think the cure can be some bungee or shock cord, or maybe little "gates" to prevent the guns from falling. Well, we did have and felt a small earthquake 20 some odd years ago....
For Federali, you do need to ask a safe door builder what he can do for you. The solution I bought is pretty good, except I removed the inner liner from the door. I never put it back on, even though my goal was to just see how it worked. It satisfied me that it was a workable modification and being lazy, I never replaced it.