If I were an instructor, I would NEVER send a student up for a solo until I had seen him cope with a completely new and unheard of situation in a competent manner.
Thats a good theory, MSP, and I understand the reasoning behind your thoughts, but there are two things I see as hiccups in this idea:
a) the student may never find himself in one of these situations, and at what point do you say "oh, well, lets send him solo now anyway" ?
a) you will eventually run out of completely new and unheard of situations, unless someone invents one... and then it's not new and unheard of.
do you know what i mean? There has to come a point where the student is "let loose", otherwise we'd never have any new pilots going solo.
Having said all that, I am an advocate for having a few more hours under the belt before blasting off alone. Experience counts for a hell of a lot more than luck...