This seems reasonable to me. I am thinking that directly on the skin might be too uncomfortable, but over the top of a synthetic t shirt (like the under-armor type), then with the remaining clothing outside of the vest it should be pretty effective.

From my experiences in Iraq with battle armor, I can say that everything under the vest is going to get wet from perspiration collecting, but the arm, torso and neck openings should serve to mitigate that under moderate conditions. A good synthetic undergarment will help to keep the comfort level up, without retaining too much moisture I would hope. You'll probably end up with fairly wet armpits if you exert yourself in this vest at all.

Step one is to get one of these vests, step two will be to find a cold place to try it out in (looks like I am gonna have to invest in a big chest freezer next).