I'm not certain, but I believe someone - July, maybe? - was ordered to PPC one of her own old fanfics and ended up recruiting. I'm not sure. I don't think there's anything wrong with the idea - after all, badfic is badfic, and it'd be a good lesson for the agent - but I imagine you'd want to wait until either your agent is sufficiently experienced to handle it or until they've done something for which the Flowers punish them.

But be careful - I don't think any PPC agents ever go into a fic for the sole purpose of saving an OC. Mary Sues and Marty Stus are often unsaveable - it's usually the bit characters we recruit. Your agents would probably have to go in and make the decision to recruit him while on the mission, not beforehand.