Eh, shove an option into a tap tree leaf and let wallets embed a backup key there for zero cost - don’t need it? Don’t use it. If/when Q-day comes (or secp gets weakened by traditional computers) ...
To be clear, you're thinking of deriving a second (hardened) key, for which a signature is checked in tapscript, assuming that the keypath spends will eventually get disabled? To do that we need a BIP32 path standard, and get this advice into BIP-0341 instead of the current advice on unspendable script path selection, then get wallets to implement it.
Things which actually use tapscripts need to decide whether they need to do this (is the loss of keypath spend fatal, or merely inconvenient?). This also needs a clear warning: that you should anticipate loss of the keyspend path...
Things which actually use tapscripts need to decide whether they need to do this (is the loss of keypath spend fatal, or merely inconvenient?). This also needs a clear warning: that you should anticipate loss of the keyspend path...
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