Hi,
You can set up a second Cisco Media Group with, for example, one or two IVR channels. In the application associated to the CTI RP, you could add the new Media Group as 'Secondary Dialog Group'. Or you could add a new CTI Port to the 2 CTI ports associated to the CTI RP in order to have a Pool of CTI Ports with 3 channels.
After that, you have to modify your routing scripts in order to check how many calls do you have in your CSQ (calls waiting + agents talking). If the calls are equal to 2, you could redirect the call to the selected extension (your operator extension).
Hope this helps,
Juan Luis