Show only on selected / All except selected

This module is great! That said, it could really use some upgrading regarding the domain selection.

Status quo

at the moment, editors have the choice to either:

1. publish content on all domains
2. publish content on positive-selection base

This mode seems to be fair enough for most use cases (as I could not find an issue targeting this problem).

However, if domains are subject to change (or worse: frequent changes) variant 2 (publish content on positive-selection base) soon starts getting bothersome as editors have to go through all content that is ought to be published on all but say 1 specific domain and have to add the selection for the new domains.

Feature request

I would like to propose the addition (replacement for variante 1) of a negative-selection base - hence: publish content on all domains except selected.

What would it need to accomplish this task?

I'm willing to contribute my time.

The idea originates from a patch for domain_blocks #2329093: Show only on selected / all except selected