I was confused when read your reply, but now i think i understand what you're talking about.
Your solution still falls on type 3 if you didn't mention wallet which automate the process. Even so, it requires both Alice and Bob use same wallet, unless there's standard (such as BIP) where other wallet might adopt the standard.
If you were setting up a dead mans switch for your family member then this could likely be agreed, and would only be a small compromise. Just like people setup wills, and trust other people to handle it after their death which is a massive compromise considering the trust factor within that. Switching to the same wallet is a rather minor compromise in my opinion for what seems to be a better solution to most other proposals.