Cry engine 3 doesnt handle indoor outdoor scenes well, notice most buildings are open few have doors in most Crysis type games you load a level it can be large but it does not handle things well in that regard.
The next thing to remember is the massive amount of quest and NPC data that as to be retained, now add in 20-30 factions that are at odds with each other, Cry Engines AI isnt well optimized for that.
Essentially Cry Engine 3 isnt used for complex RPGs for a reason
Frostbite is in House so no go there for Bethesda, even then Modding is locked out for all but the most direhard adding new content like weapons armors etc is impossible.
Unreal Engine doesnt handle large enviroments well, modding is possible but is also extremely limited As it would require custom tools which requires long development times on top of the high price to use said engine
Id Tech 5 while suitable in size and scope lacks many newer features its a good engine well optimized but lacking in what users expect offering Open GL or DX9 level visuals only at this point in time. Also nearly impossible to mod.
Cry Engine 3 good visuals but not made for this type of game. modding is possible but unlikely to flourish as tools while good are more complex again limited situation.
Most engine currently just dont fit what Bethesda needs. they NEEDED to buy a new license to the latest Gamebryo that before they went out of business granted they were bought so licenses are honored but Bethesda needs to update yet they refuse.
Latest builds offer DX11 support etc. Altho with the sale of Gamebryo the shake up in the company 2 years ago could have caused the current builds to be a mess.
