Linux netbook in a safe deposit box. Hasn't this method been around since the beginning?
Keep a deposit address handy and you're good to go without visiting the bank every time you need to add funds.
KISS
Why would you need a netbook? Why not just a USB key for convenience and a backup paper wallet in case you can't read the usb key?
Because i want an INDEPENDENT hardware wallet which i have some internal control over the money balance and supports alt currencies. I don't want the wallet to have direct connection to my main computer which is connected to the internet 24/7.
But you can plug a USB key into anything and import the wallet.
Putting a laptop into a safety deposit box, make damn sure to remove the battery first because they can and will go bad sometimes resulting in leaking that can fry the computer. Hard drives, with SSD drives it may not be as much of an issue but with platter drives, when they have been sitting for long periods of time they don't always correctly spin up and then you have to do data recovery.
You can keep just the data part on a USB key. When you need withdrawal, boot a laptop or whatever, let it update the blockchain, then plug the USB key into laptop and import from it. You don't need the whole netbook in safety deposit is all I'm saying and using a netbook gives risk of it not being bootable after sitting for a period of time thus requiring removal of drive to get the data.