This seems interesting but honestly I'm wary of it due to limited information, I'm curious as to how you intend to set this up, what the basic plot would be etc. The idea of OC's intrigues me though.

Would this be taking place after the events of Portal 2, or between the two games? Alternatively they could be happening simultaneously.
Do you intend to have characters solve puzzles as subjects or operate as scientists pre-GLaDOS?

Above all else, it seems like it might be [s]very[/s] difficult to write out how the portal system operates in itself.