So they have a beta version available for the PC version and a mission editor (ME)(very complex) is included in this beta! The worse thing is that they didn´t included any manual for the ME, though gameshoes have made some youtube vids about the ME. There is a sub-thread over at Gaijin forums about the ME:
http://forum.gaijinent.com/index.php?/topic/3706-editor-post-your-experience-and-discoveries/ (you have to be registered there to have access to Beta sub-forum though)
What I can see from the tutorial vids is, that we have a lot of possibilities with it.