List Emailing is an essential functionality when working with Campaigns. "Accounts as Campaign Members" feature (although Beta) would benefit from addressing this in one or multiple ways. 

1) Clearly stating in the documentation that currently List Email will not send emails to Campaign's Accounts themselves NOR Contacts related or affiliated to the added Accounts (without this in the documentation, I spent weeks working the case on this with SF support, and they never directed me to this page)

2) Putting it on the roadmap to enable the inclusion of Contacts related or affiliated with Accounts in Campaign into the List Email

3) Putting it on the roadmap to include a button in the "Accounts as Campaign Members" feature that would allow adding all Contacts under all Accounts in the Campaign into the same or Child Campaign

4) Building in capability to add a filter to a Contact report or List View that would allow filtering by an Account's Campaign membership (an Account that's either Related or Affiliated). Such report or list view will allow adding all the Contacts in bulk to a List Email (from list view) or to a Campaign.  (Reports based on Campaign Member object that can show Account members and their direct Contacts do not allow adding Contacts to a Campaign)