think you'll be OK, lets see,
Aileron, Elevator, Throttle, Rudder, Fight mode, leaves 1 channel for either OIC or Failsafe (RTF/Autoland). If you dont want to use manual mode you can make RTH your third flight mode (GPS,ATTI and RTH) I take it the DX6 has a 3 pos'n switch. You'll need more channels if you want gimbal/camera control.