This is an interesting use case. You're basically describing a simple smart contract, along with a bit of social scaffolding for it, e.g., Bob + Alice who want to transact, and then some third-party arbitrator who's also on the contract to keep them honest.

It's important to recognize that the "code as law" people misunderstand something crucial, which is that these things are social problems, not technological problems. Whatever smart contract a person describes, you can think of edge cases that require some kind of adjudication, and to describe how that adjudication would work, you've just re-invented an ad-hoc and less predictable version of contract law. There's no free lunch on this stuff.

Even so, ideas like this are cool because what you're really doing is lowering the bar for quasi-legal services. For instance, right now, for small amounts, Bob and Alice have no practical recourse for these kinds of guarantees -- they could get a legal contract, but enforcing the contract would be so expensive that, for all practical purposes, they'd never bother. Smart contracts, including this multisig variant, change that calculus. The implications are evocative, even if it's not the utopia that many imagine.

Also: you should consider posting these ideas in a separate post. The Operation Saylor thing is fascinating in its own right, but your thought experiment deserves a wider audience who may not find it buried in the OS update.