It would be great if there is an action to subscribe subscriber to list 'B' after subscriber receive all the list 'A' autoresponders or (it would be greater) after subscriber receive the certain campaign.

Why?

Sometimes it's necessary to set up the complex campaigns combination to explain to subscriber the wide subject _sequentially_ and not to subscribe to all lists but to one list, then to second, etc. The lists sequence may be different and based on interests (fields) chosen during the subscription.

Email marketing is not always about to send some letters. Sometimes it is the complex thing, even educational process.