Silly question, do you have kids in the house? A wife or signifigant other?? Is the SO gun savvy?
If there are kids you have got to store it so it is accesable to you but not to them.
Why rotate mags? The posts here say you wear out springs by "cycling" them not leaving them either loaded or unloaded. If I needed a handgun for SHTF I would want 2 mags. minimum ready to go. They say when auto loading handguns fail to operate properly it is usually due to mag. problems.
However you store it make sure you are sure what state it is in, nothing worse then pulling the trigger and nothing happening, or ejecting a live round because you racked the slide on a loaded chamber.
I just bought a Mini-Vault. It is real secure, real secure, and relatively fast to operate even in the dark. The downside it is kinda small and cost $140+. It does allow for a variety of mounting options, has a user settable combination(lots of possible combo's), and also work with a key.
Of course YMMV, and just throwing some stuff out to see if you can use any of my ideas.