I had the same problem on a fire-rated double door to a commercial kitchen.
Three possible approaches I can think of:
1) A custom door panel that fakes it in 3D, and then add a fill in plan. It's not that hard if your door panels are equal width, if not, it has to be coded manually. 2D needs to be faked in.
2) A regular double door with a column object in the middle, that takes care of the plan view and 3D. 2D same problem as above.
3) Place two ganged doors in the model like you said, but exclude them from scheduling and use a separate, hidden double door that will appear on the schedule instead.
I felt lazy so I did #2 but it all depends on your comfort level. #3 may actually work best.