Ha.
Having a belief in God doesn't mean putting my brain on the shelf.
And having a secular explanation for Paul's vision is not a problem, because God works via ordinary things. I have seen miracles, but I have also seen "coincidences" or improbable cures or episodes that changed people's lives but that could be explained scientifically or by chance, but just because there could be a scientific explanation doesn't mean it isn't God orchestrating the episode.
So Paul may or may not have hallucinated from heat stroke (or gotten a temporal lobe seizure from dehydration and hyponatremia), but God arranged the medical problem so that he could direct the vision to change Paul's life.
A modern example of this would be George Forman's vision of Jesus (after a prize fight, where it might have been from electrolyte depletion like Paul or maybe from a slight concussion) but the fact is that this vision of Jesus changed his life for the better also.
And John Paul II's visions when he was semicomatose after the assassination attempt probably led to his actions that helped cause the peaceful fall of communism.