A different aspect, that I think @rkuhn mentioned at some point, is if references to the processor itself should be stable after recovery (stop/start), i.e. the processor actor always gets the same uid.

To me it is not clear what implications that would have. E.g. watch/Terminated.
I think it would also be complicated to implement, as the uid is assigned before the actor is really created.

Anyway, all this needs discussion, and we might not be able to make it perfect in the first iteration.