Some observations and opinion...
Early GM MEFI used a central plenum location.
GM abandoned that location years ago. Most GM IAT's seem to be either in the airbox or the intake tube upstream of the TB.
All locations are a compromise.
I'll agree that the closer to the valve, the more potentially accurate the reading, but its not realistic with current technology.
If your tuning is such that you can keep you're AFR's consistent with varying temperatures, you've won, regardless of location.
Transitional pressure changes shouldn't be an issue if the filter settings are correct.
The insulation idea, used in conjunction with a Bosch style sensor, might backfire... if its heat soaked long enough to bring the insulation 'up to temp', it will take that much longer for it to return.
I was looking at the Audi 1.8T IAT sensor and it seams very well isolated. Might have to snuggle up with it...