I have been trying to figure a way of hiding guitars when away. Could involve some fancy building reconstruction...
I've lived in a lot of places. A few ideas I've done before and still do.
* Install an exterior grade locking entry door knob onto a bedroom door and keep your guitars in there.
* Reinforce the interior of a closet in the basement under some stairs with a lot of extra lumber. Reinforce the door too. Install some tamper proof metal plates which block access to the hinges (they sell those). Then install an exterior grade locking entry door knob onto that closet door and keep your stuff there.
* Keep as much of your guitars and gear hidden when contractors and service people come over to your house. Make sure all doors are still locked when they leave (especially the doors you never use).
* Install exterior lighting and security cameras. Aside from the usual plain sight snatch & grab stuff which sits in plain view all the time, specialty items such as high dollar stuff like guns and guitars are usually stolen by a family member or close friend who knows they are there and where to find them.
* If you have a big huge gun safe, KEEP IT LOCKED 24 hours per day. (Or any safe for that matter.)
* Remove exterior foliage which will allow a burglar to hide in the bushes unobserved from the street.
* Become a dog lover and get a big doggie (over 40lbs). Research the best breed for you. Either a "guard dog" or an "alert dog" will greatly help protect your stuff.
* If you are an NRA member, put your membership stickers at each entry point to the house or on windows most likely to get smashed with a brick.