So, I don't know. Big Boss still has an MSF patch on his shoulder during the ash-smearing scene, so I imagine that's the point where he abandons MSF and decides to start up Diamond Dogs. But then all the Diamond Dogs training scenes (you can tell by everyone wearing Diamond Dogs insignia) are set on that same oil rig. Maybe it's like a Forward Operating Base for Outer Heaven? Maybe this just is Outer Heaven?
Hi, in the burial at sea scene Big Boss is wearing the MSF insignia on his right shoulder, and the Diamond Dogs insignia on his left, much as how he used to wear the FOX and MSF insignias together despite at that time only being a member of the former, and in the same way that Meryl wore the Foxhound insignia long after it's disbandment.
I imagine Big Boss will sport the Diamond Dogs and MSF insignias together through most of the game, right up until Diamond Dogs gets blown the fuck up and Outer Heaven finds it's home in Africa.
If you need help peicing the scenes together, keep in mind that:
---That scene of a massacre with Big Boss covered in blood and any scene involving the african boy probably take place in at least the second half of the game, since it seems Africa is the second open world area after Afghanistan.
--The scene where DD's soldiers are acting like zombies most likely takes place towards the end of the game because if Big Boss is wontonly shooting his own men then Diamond Dogs is probably falling apart/in shambles at that point.
---Maybe the cremation/burial scenes take place after this event, and whatever causes them to become zombified (Psycho Mantis???) is how those soldiers died in the first place.
---the segments involving Eli/Liquid most likely take place earlier in the game since Liquid is already known to have spent his youth in Afghanistan.
Hope this helps. I'll edit this trailer in with my old MGSV Chronological Megatrailer shortly, I'm just waiting to see if there's an extended version.