Sabin Duvert
My only concern would be when it comes to situations like breedings or customs where the colorist is given the task of a pet to complete at a later date. Part of the consideration when it comes to new colorists is reliability, and the last thing you want to do is have a guest colorist lose interest and flake before completing a breeding.
While maybe a guest here and there isn't a bad idea, I would vote for it being for pre-completed pets alone. ((ie, they're completed before given out - like for an event or flaffle or something like that)).
Actually looking at this post again I realized that maybe breedings could work...they'd just have to be chosen off the Master CC list beforehand with only the staff members told what was happening. If the guest flakes then no one but the staff would know and no one is owed a breeding.