The email I was talking about would be a single email sent from bpo, listing all issues you created/followed/are assigned to. This would be especially useful for occasional contributors that follow at most one or two dozen of issues, since they can go through them, review them, and resubscribe manually (if they are still interested).
However I do realize this is not ideal for very active contributors like you (I’m in the nosy list of over 4000 issues myself, so I definitely hear you). I’m still looking for a better solution that would allow to either preserve the nosy list subscriptions, or restore them after the migration.