Currently it is not possible to add tables between bases without loosing the link between the linked tables. Since it is easy to Duplicate a Base now, it should be easy to combine 2 bases together.
Benefit of this would be to have control of the structure from one base to another.
Example: You have many bases that you need to combine without starting from the beginning. Right now we can use Zapier to move data around but nothing to control structure of the tables.