Very good idea! Much like the Great Artist Culture Bomb ability. Except GEX Mapping ability would reveal random area from somewhere on the map (like maps from Ancient Ruins do). I believe there is potential for the Great Explorer (GEX) unit.
Great Explorer
Every explored hex counts as one point (like combat points for Great General) and when you have suffient amount of exploration points, the Great Explorer will appear to one of your cities.
Abilities: Gives Movement 3 and Ignores Terrain Cost. Has a large sight radius and gives+1 Line of Sight to friendly units in adjacent tiles. Ignores Zones of Control. A high retreat chance. Double yields (30 or 60 Gold) from finding new friendly City States. Double yield from Pillaging Barbarian Camps. Double yields from discovering new Natural Wonders. (A huge plus with the Spanish!

)
Improvement: Cartographer Yields: Gold, Science and Exploration points which count for new GEX to spawn (EPs works much like GG points)
I see GEX could potentially be the only Recon unit with Scout. Other units just would not be needed. Though the downside of GEX is that it doesnt have any combat strength.
Awesome idea. Is there a possibility for new Recon unit in G&K ? I do not think they have released in on the all new units yet. Ill keep my fingers crossed for this one.