If, as you say, there is the room for a second Soyuz issue, then that first idea to use te ATV and the Soyuz both as rescue vehicles becomes quite interesting!
The ATV will anyway have its own docking port.
If only one guy is to be trasnported back to Earth, it would happen with the Soyuz and 2 (or 3 astronauts) could go on maintaining the station, until the next Soyuz capsule docks to the Soyuz docking hatch.
If another type of emergency would arise, requiring the immediate return of another crewmember, then there is a problem.
But two separate similar emergencies within several days? That's quite stretching the odds!
There was a situation like that, with Salyut 6 in 1979, I believe:
Ryumin and Lyakhow were sort of stranded in space, after the Soyuz 33 (with the Bulgarian Ivanov) failed to dock; they had to wait until an unmanned Soyuz 34 was launched, just for the purpose of returning them back. They wanted to spend 175 days in space and didn't trust the reliablility of their Soyuz 32 vehicle that returned unmanned.

Raoul