Well, unless those final wishes are to be stored in LN2 in Detroit. That seems to contradict your thesis, appealing as it looks at first glance.
The whole point of cryonics is to ensure it’s NOT your final wish.
A paradox!
It’s their final wish if and only if we do not comply with it. But we should comply with it if and only if it’s not their final wish. (The latter ‘only if’ requires some external reason, such as waste of money; of course we assume that the relatives who make this decision don’t believe in the promise of cryonics.) Therefore, whatever we do will be immoral, one way or another.
A paradox!
It’s their final wish if and only if we do not comply with it. But we should comply with it if and only if it’s not their final wish. (The latter ‘only if’ requires some external reason, such as waste of money; of course we assume that the relatives who make this decision don’t believe in the promise of cryonics.) Therefore, whatever we do will be immoral, one way or another.