@julian @PortaFed
giving a further read: I can't really imagine a case where someone would a) regularly be creating signed backups and also b) know in advance where you wanted to migrate to to set the destination_did. Like if this is for the case where the instance has shut down, you might have some signed backup, but you probably haven't planned in advance where you would want to migrate, and if the instance is down you wouldn't be able to create the migration object after the fact.
the validation strategy for the export is sort of mystifying to me. if the whole object is signed, then why would you need a merkle tree for objects and also an object count? if the contents of the object have changed post signing, then the signature validation will just fail and those are irrelevant.
true to form for LLM generated documents, several critical things are left undefined, like what last_accepted_sequence is or how that works.
probably the most important problem is that it's not really clear how all other instances are supposed to handle this, which is the entire hard part of a migration spec. Like, if the purpose here is to preserve identity, then you would need to have all the other instances come to see the new identity as being equivalent to the old identity, and there's no discussion of how that process works for third-party instances at all. like e.g. in FEP-1580 i had to spend a long time gaming out scenarios for how third party instances would handle a move event.
so without that it's not really an account portabiltiy spec, it's an account export/import spec, which is fine, just not really needed since signing objects and collections (which this spec should use anyway) is already described by other specs.