These steps don't seem to be necessary. Since the CM can be opened from the inside towards the LM, the third astronaut could just wait in the LM and be let in that way.
I think the only question is really how quickly can you repressurize the CM.
It was basically a cone-shaped pressure vessel 3.23m tall and 3.91m wide, that's 51.71m^3 of volume. I'd estimate about 50% is taken up by machinery, so how fast can you repressurize 25m^3 to 1/3 sea level (which was apparently standard for the spacecraft)?
My guess would be it could be done pretty quickly, maybe 2 minutes?