Is it possible to do any kind of vaulting with some clever taproot script path spends? If so, what are the fundamental differences of that vs vaulting with OP_VAULT and what improvements does it provide?
Discussion
OP_VAULT is a covenant, which does not currently exist in bitcoin. A covenant is a condition that controls what addresses your coins can move to once they leave their current resting place (locking script). Currently in bitcoin, once the locking script is satisfied, the coins are free to be sent to any address (or burned or sent to miners).
You can achieve a similar effect with the current bitcoin protocol by creating a signed transaction and throwing away the private key. But this solution is inherently complicated, inflexible, and it's impossible to prove that it was done correctly after the fact. These obstacles mean that it probably will never achieve widespread adoption.
OP_VAULT is a dramatic simplification of this process that adds back all the flexibility you lose in the pre-signed transaction case. And it is dead simple to prove on-chain. Simplicity is tantamount to security.