Maybe I'm wrong about this...

But if you pass bitcoin down to someone in the future, wouldnt it be way easier to just write down your seed phrase and keep track of it instead of trusting a firm with custody of the keys to your stack? Don't get me wrong it just sounds like an over complicated setup with multisig. All your kids or grandkids would have to do is just obtain the seed phrase instead of waiting for a timelocked stack to unlock.