There are three types of subcontracting plans individual, master and commercial under the Federal Acquisition Regulation (FAR) at FAR 19.701. The contractor has complied with the requirement for a subcontracting plan as you state that he has an individual plan that is approved. Under FAR 19.702, the contract only requires one subcontracting plan and the type of plan that is applicable is at the contracting officer’s discretion. I would conclude from the information you provided that the contractor needs the approval of the contracting officer as he is making the request as part of an option exercise, an action by the Contracting Officer not the ACO.
I would proceed with the exercise of the option as written citing the approved Individual Plan. If the Contracting Officer then wishes to move the contracted effort to the approved Commercial Plan, that should occur after the Option is exercised and once there has been an agreement on the appropriate amendment (if required) to the approved Commercial Subcontracting Plan. Since the Commercial Subcontracting Plan normally covers a fiscal year which may or may not coincide with the period of performance of the subject contract after the option is exercised.
I also recommend consulting your local Small Business Administration Administrator (SADBU) for assistance.