I can understand Kwan's reluctance to commit to doing the GP. It's not the events themselves, it's the fact that there would be (likely) THREE events (SA, CoC, GPF), two requiring lengthy travel, and one of those just weeks before Nationals. For a skater who hasn't been doing much early season competing (cheesefests, with just one FS, no SP, no exhibition), that is a huge change of pace---and one that might, indeed, cause pain and injury.
Michelle has mentioned off-ice training, and it may be she will do that even more intensely this season to build up her body and fend off injury.
And you can't compare Irina and Michelle. Irina did not compete at all from the GPF in 2003 until Worlds 2004, and was confined to bed for much of that time. Her body did get plenty of rest and recovery time, even though she may not have welcomed it. This past season, Irina was very strong in the early season, but her later performances (GPF, Nationals, Euros FS, Worlds QR, SP) she wasn't skating as freely as she had earlier. Her spectacular performance in the Worlds FS no doubt owed much to sheer will and adrenaline skating in her home country.
Irina competed the entire last season with a muscle strain in her knee. She has not allowed aches, pains and exhaustion to interfere with her competitive schedule, and that is because she has a chronic illness and faces a future when she may not be able to skate at all. Irina has indicated an interest in becoming a TV commentator after she stops competing, so she has already made plans for an off-ice career after Torino.
Michelle, with a long pro career in the offing, has to be concerned with the condition of her body.
But I do hope she will commit to doing the GP, because she needs to execute the CoP choreography many times in competition in order to gain the muscle memory she must have to deliver a brilliant performance in Torino. Perhaps she would be best focusing on refining her CoP choreography during the GP and not be concerned with winning medals (and then she wouldn't have to do the GPF!). After all, Kostner pretty much bombed the GP last season, and it didn't keep her off the World podium, while Rochette won three GP medals and faltered badly at Worlds. And Cohen has won over and over in the GP and then had less than spectacular results at Worlds.