IAS are trained in a particular fashion and definitely are the cream out of the students today. Their intelligence and management skills are quite good and well above the standards of non IAS stream persons. State government should not do experiment as that could lead to mismanagement or not a very good show of administration by the so called non IAS managers. The non IAS managers are generally good in their own core area rather than having a generalist view.
Knowledge is power.
The standards of IAS pass outs will be very high and I feel merit only play an important role in the selections. No corrupt practices. (If I am wrong somebody can correct me). So all IAS officers will be very good administrators. If there is a shortage of IAS officers also we can't fill those posts with non-IAS people.
The states should not indulge in such practices. Already the ministers are spoiling many things. In addition to that these non-IAS officers appointed in IAS posts may add ghee to the fire. The central government should see that the state government will not indulge in such practices.