Personally I think it wouldn't be so hard to create a program that takes screen snapshots every time you click that also records the mouse position and then saves it ready for sending to the external party later if you are currently offline (so again it is not anywhere near as secure as actually having an offline computer).
BTW - Armory or hardware wallets like Trezor aren't the only solutions - apart from "paper wallets" which you could create offline I developed the CIYAM Safe (https://susestudio.com/a/kp8B3G/ciyam-safe) for doing 100% secure offline txs (using QR codes rather than plugging in any cables between the online and offline computers).