I think it would just be better if you hid your chests better. Don't put your valuable items in your base. Instead, run far away from your base, find a secret area you're certain no one will come across by accident, and put your items there. Some good places include deep underground (perhaps underneath lava), at the bottom of the ocean, and if you're daring, in the Nether or End.
Locked doors probably wouldn't have any uses in adventure maps as we have iron doors already, and servers could use plugins if they wanted.