It is unnecessary to use hashed timelock contracts if you can use simple a simple timelock value in transactions.
You shouldn't make things more complicated then they need to be.
simply, just in the case Alice has complicated scenarios for her will.
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but there is one serious question here about "Transaction malleability":
https://en.bitcoin.it/wiki/Transaction_malleabilitywhich of solutions above are not vulnerable to malleability?
Transaction malleability doesn't influence the scenario and the outcome of the transaction.
What transaction malleability basically is, is that you can take a broadcasted transaction and change a 'value' (not possible to change receipent/amount/fee) to generate a new hash ('basically same' transaction, just a different hash).
This is a problem for not-that-good coded exchanges which rely on the transaction hashes when withdrawing funds.
But this doesn't have any influence in this scenario since it doesn't change anything important.