Heres a couple of other thoughts:
theres room inside the dash to the left of where the glove box "box" tilts into.
Open your glove box, flex the sides inward to get past the little retainer posts and tilt it farther forward and it will lift off, look back and to the left and theres a nice, med-large handgun sized slot there.
Just gotta figure out access.........
Also another spot for a James Bond slide out affair might be the dash itself.
On both sides, if you look at the bottom, theres a center panel about 3" tall by maybe 12" or 14" that looks like its part of the dash, its not.
It's a rubbery plastic panel that pops on/off on both sides with a fair amount of room behind it.
Could be a perfect "drawer front".
Something tiny like my KelTec PF9 9mm is less than 1" thick and still carries 8 rounds of 9mm hydrashock goodness, lots of little hidey hole possibilities for it
Just tossing out some ideas here.