Like I said we can agree to disagree on Geopolitics and History.
I disagree that Serbia would automatically go for Russian option., after all the country has recently bought some western equipment (Landrovers , HUMVEEs etc) and has swtiched to NATO standard ammunition. Reality is that West will not sell Serbia anything advanced, and Serbia CAN not afford it anyway. So China / Russia are only option.. with Russia more willing to be flexible when it comes to payment.
As you have said Radars are number on priority, however the need for advanced medium / short range AD is still there for security purposes. Jets can not compare in their cost effectivenes if one has to defend airspace against vastly superior forces. For simple air policing 4-6 jets Be they MiG29/Rafale/Gripen/EF/J10 or even JF17... they will all do just fine and you dont even need long range AAMs.
I read somewhere that BukM2 battery is 4-5 Million ... for price one one MiG you can get whole squad of 6 units. There is no argument which is more effective of protecting your arispace. Combine Buk with Pansyr and you have incredibly capable integrated Medium/Short range system that can take on Aricraft and provide point defense against Cruise type missiles.