then an FAI constructed from our current CEV would give weight to their preferences once it discovers them.
If they are to be given weight at all, then this could as well be done in advance, so prior to observing aliens we give weight to preferences of all possible aliens, conditionally on future observations of which ones turn out to actually exist.
From a perspective of pure math, I think that is the same thing, but in considering practical computability, it does not seem like a good use of computing power to figure what weight to give the preference of a particular alien civilization out of a vast space of possible civilizations, until observing that the particular civilization exists.
One such regularity comes to mind: most aliens would rather be discovered by a superintelligence that was friendly to them than not be discovered, so spreading and searching would optimize their preferences.
If they are to be given weight at all, then this could as well be done in advance, so prior to observing aliens we give weight to preferences of all possible aliens, conditionally on future observations of which ones turn out to actually exist.
From a perspective of pure math, I think that is the same thing, but in considering practical computability, it does not seem like a good use of computing power to figure what weight to give the preference of a particular alien civilization out of a vast space of possible civilizations, until observing that the particular civilization exists.
Such considerations could have some regularities even across all the diverse possibilities, which are easy to notice with a Saturn-sized mind.
One such regularity comes to mind: most aliens would rather be discovered by a superintelligence that was friendly to them than not be discovered, so spreading and searching would optimize their preferences.