Barca probably has enough nobles (or will have enough) to maintain 2 more regions. The obvious choices are Nark and Kydonia, as both are still semi-close to the capital, reasonably supportable by allies, and, if taken, they leave Rettlewood sheltered from major attacks. If Aurvandil took Lusitania and Barca took Kydonia, then Celtiberia would be sheltered as well. Under such circumstances of rising population, good allied support, a ready market for food, and no immediate monster threats, Celtiberia could become a major food exporter.
In fact, Celtiberia has the highest food production of any region in the currently settled Maroccidental realms. Nark and Kydonia (then Aurvandil in Lusitania) would allow it to become a goldmine for Barca and significantly shorten Paisly's supply lines.