My GZE'd sprinter has a bigger radiator (not sure how big but pretty big) and a 14inch thermo behind it. If you run the intercooler pipes (for a front mount) the right way, you should be able to squeeze the aircon in, but my engine bay is packed, even though i have no aircon, with a thick frount mount. If you put the intercooler as forward as possible it should fit behind it. but it will be tight!
As far as the radiator, you should upgrade to a bigger one because the GZE will overheat tremendously at long idles. It won't really effect airflow if the intercooler is in front of, just connect the thermos to your air-flow sensor!