Read this thread where a passenger was trying to do a similar thing but through DEL. The outcome was not good.
Denied Boarding DOH-DEL-DOH-LAX
If your travel is in the near future then I agree that with heightened security a three hour turnaround may be tight if you need to go airside. I understand the CMB authorities are asking passengers to be at the airport four hours before the scheduled departure time of their flight.