Do I miss something?
What are possible attack vectors here?
One big attack vector would probably be the most obvious. Physical access. Until you are not living in a bunker and depending on the amount you store this would be an efficient attack vector.
Since your plan does not mention any backups a "simple theft" of your harddrive would be an option.
Another way to gain access over your private keys is to infect your pc which is connected with the internet.
If you have a big amount stored and an attacker is targeting at you it probably wouldn't be that hard to get malware on your pc which will infect the usb stick.
And once USB is infected and you plug it into your cold pc to sign the TX the private keys could be copied over to the usb without you noticing it.
And the next time you connect it to a pc with internet connection (e.g. when you want to push the TX) the malware automatically pushes a TX of all your coins to his address even before you can start pushing your TX.
Of course this is more theoretical nature. But its definetly possible. Noone would put so much effort into it for 1-2 coins.
But 100 BTC are pretty attractive. Big Big Holders should definetly be careful about giving too much personal information away.
