I'm not the right person to ask really. I tend to not think about soft forks and op codes much (I find the social dynamics around them more interesting than the technicals). I also don't spend much time thinking about improving the store of value properties of bitcoin because it seems like that's what most bitcoiners think about.

In general though, your thinking is good imo. Multisig setups like this make it clear what vaults would give that we can't achieve by other means.