Ouch, this part in your Ajax plugin seems really difficult to understand for me ... :(
But even if I'll understand it, I'm always wondering how I will be able to return this boolean in a "Check thing" action...
If you have time, I could send you this part of my code in order to make you understand exactly what I want to do (I'm adapting an external library so I depend of this library)
Edit. Ash, I sent you a personal email since my plugin isn't released yet, but I'll give the solution asa I'll be able to correctly understand this.