Well there are a lot of good points here.
This may sound silly but I had not taken into account the exposure to the sun.
I was basing a lot of my ideas on those cool suits that are made for race car drivers.
I suppose some of the open cockpit cars do see some sun but may not have the same exposure as a motorcycle rider.
To make more efficient use of the suit's cooling I would imagine that some insulation would be appropriate.
I could also imagine that the wind would do a good job at balancing out the sun's effects while in motion.
The Stirling unit I am using is capable of about 150 watts of heat lift and only weigh about 7 lbs.
This is a lot lighter than the ice water pump systems used in some race cars.
I don't really expect to be completely cooled in every riding situation I would just like something that can help out in keeping me cool during average city riding while wearing complete safety gear.