I have always thought that areas like no magic or wild magic present a higher challenge for a given CR than "normal" areas. Would it be feasible to provide a bump to kill xp in those areas? In other words, if you kill a CR 17 Large Snake in a no magic area it would give XP as if it were maybe CR 20. This would reflect the added challenge of facing creatures without mind blank, mage armor, haste, etc.
I realize this probably isn't a realistic thing to include in V3, but thought it might be worthy of consideration in the new game.