Khosaru II is gonna get his hands on more money, you need to wait and see how exactly
Also on a side note, keep in mind alot of Romans hated Phocas because he was a tyrannical leader. Some romans would defect i bet, especially if this Khosaru is more tolerate to Christians (POD involves him getting another Christian Wife)
They were angry with Phocas but them defecting to the Persians when they know Khosrau is going to take them over is not going to happen, at all. While the tolerant decrees in 409 would ease tensions among such sects as Armenians and Nestorians I doubt it would make the Romans happy.