Where online, there is such a thing as hacking and if hackers trace that your coins are online they will try to hack it, what's the use of hardware wallets if keeping it online is safer and about OP's offer, this is for those who want to keep a huge amount of Bitcoin because it's not cheap.

I believe a safe where you keep all your important documents is preferable there are people who keep their coins in a vault and it goes how they protect their vault from criminals, a vault is hard to open and penetrate because of its security features it is not cheap but at least it includes all your important documents because its bigger.