The OKO is an excellent reflex sight; I like mine better than I did my Aimpoint COMP-M XD. But by the time you invest in the sight, the roll cage and a gooseneck mount, you're talking darn near the same money! :-o
The other problem is that one of the OKO's W/E adjustment screws is located on the back of the sight body - mounting it in a gooseneck mount doesn't allow enough clearance behind the sight to adjust the screw (A2 handle is in the way) without fabricating a dedicated tool (like a bent screwdriver shank).
I've known plenty of folks to have good luck with an ARMS-style carry handle mount and a BSA or Simmons 30/42mm "beer can" red dot - at least until they decide whether or not they want something better or more advanced. For many, an inexpensive setup is all they need for casual applications; not everybody is using their AR to defend themselves or save the world. Those that ARE, certainly should have the best gear they possibly can!