There's actually something similar to this in the presidential motorcade. One of the Escalades basically has no passenger seating and instead is more or less a pretty version of a Stryker. There was a discovery channel thing on it years ago, wish I could find it.
AFAIK the ones still in service are highly up-armored and the gunners wear a big bullet proof suit.
The gun itself doesn't retract but it has armor plate to protect the gunner.
I mean, this is some cute little merc toy to make rich drug lords feel safer, but I imagine the gunner could be pretty easily killed with some lucky shots from an AK 47 with armor piercing rounds. Or depending on gunner equipment, just a lucky/good shot to the face with anything.
This is really more for escorting rich western contractors through war zones to oversee their operations exploiting foreign peoples in their own countries.
Dictators prefer classic and rare cars filled with soldiers and utterly ruined with gold plating and hydraulics, and aren't in a massive amount of danger from their own subjects usually.