Possible to run "hard moderated" lists together with public lists

This question is slightly related to the two threads about unsubscribing to single lists/specific lists (Unsubscribe only for specific lists & Unsubscribe from single List)

I’m wondering if there is some way or any plans to add functionality so you could have a strictly/hard moderated list.

Our organization has the need for a member registry, which is something we would do manually by adding and ensuring our member details are up to date. This member registry is to be used for invitations where it is required that all members are sent copies, no matter if they really want them or not (which I know is bordering on spam, but it is regulated by law in our country that these invitations are to be sent to all members of the organisation), so unsubscription from these should not be possible for the members themselves to perform.

In addition to this strictly moderated list, we also have some parts where we want the members to be able to opt-in and opt-out based on their interests and level of activity.

Both of these work just fine to do in their separate phpList. So, if we would run two instances of phpList both of these would be possible to do. What I’m looking for however is the option to have both of these in the same phpList instance, not having to have double the instance to do backups on, two databases, two sets of phpList to update etc. Also, for the people that are to be using them it is also a lot more confusing having two setups of the same software, both looking identical…

The issues I see with it is kind of related to the two other threads I listed in the start. What I’m guessing would be a requirement to be able to achieve this is to move the blacklist from email address level to a email address/list combination level, so that upon unsubscribing from one list the user would still be able to receive emails from other lists in the same system.

Also, the behavior of unsubscribing the user from non-public lists automatically is quite confusing as there is no indication to the user that this is going to happen…

Customizing phpList to achieve this, what would be the best way forward? Rewriting the actions when unsubscribing to make sure the private lists are excluded?