you know how the Klingons are isolated, but can't go into areas near the Sol system (they have to go into Other systems around Sol to get to Cardassian space)? that's how they could build the Romulan race.
With the Romulans, you can't go into Klingon territory for example. But, for example, you can build your espionage skill which would allow you to land on any planet for specific assignments. I just thought of that. That would be an awesome idea