Here's a possible solution if you're happy waiting a long time:
For some background, the rationale of the existing limitation is explained here
The reason behind the design choice was this:
A dacpac can be published to any database -- empty or non-empty. And
when table data is published, if the target table isn't empty, all of
the data is dropped and replaced. But if the target table isn't empty
and it has incoming FK dependencies, then there could possibly be
broken FK references. Requiring that all tables be a closed set
resolves this problem, because any incoming references will be erased
This isn't the only design decision that could have been made. For
example, we could modify this logic to allow incoming FKs from tables
that aren't exported, and then perform a pre-deployment check to
verify that there will be no incoming FK reference issues.
For my purpose, I'm trying to create a seed database for developers to use setting up thier local environments, this means I'm deploying to empty databases so the FK's don't need to be a 'closed set'. I only want some lightweight reference tables populated.