I think that the idea of the Exiles' being able to research Starbases, without being able to make use of it, can work thematically too. Presumably the Exiles have had to master the technologies required to build both Starbases and Orbitals independently before they were able to construct their own special Ships. Hence, the choice to research the "basic" Starbase employed by the other races is a curiosity-based driven research goal, rather than in the interest of constructing them.
Just an idea.
Just an idea.