It's not without its own issues but wouldn't a passphrase derived from the main seed words not written down help with this to a degree? They could find the steel with the seed phrase but you could have any number of wallets on top of that seed. 

poe7645

247bf84fda

bitcoin

The best ways to store your seed phrase/private keys when it's offline

btccreative21

I dont find paper/steel wallets safe. If a thief, or the government/police, or even a "friend" / family member, has access to it, it's game-over.