Your Wildest Theory about Season 5

Really?  I can speculate off the wall?

It is 2022.  Fitz is working on the time machine.  In the room with him is Jemma, Coulson, Daisy and Mack.

Fitz makes a breakthrough at the same time the Kree arrive at the lighthouse.  A Kree guard invades the lab, Daisy, Mack and Coulson see it as a threat, and during the fight, the machine is accidentally activated.

Daisy, Mack and Coulson kill the Kree, but the machine can't be stopped.  All five plus the Kree body gets transported to 2005, which is why we don't see any of them after Robin's third flashback.

In 2005, Coulson knows exactly how to contact Fury.  Fury arrives, debriefs the team.

Before Fury can get information from the team on the near future, Ghost Rider shows up and claims Coulson, but the entire Team goes because it's the way for them to cross dimensions back to 2018.

Fury now has a Kree body with the knowledge that not only can he create a serum that will bring someone back to life, (i.e. Coulson), but knows to put Coulson (in 2005) in charge of the GH program.

The team, now in 2018 has a second chance to save the Earth and succeeds.

Everyone lives happily ever after, or at least until the second arc of the season starts.

Enoch, on the other hand, meets up with Mr. McGuire, and travels down a whole 'nuther path.

(Well, okay, it's full of holes, but just as plausible as beren44's. )
(Oh, and if you got the Enoch joke, then congraduatetions.  HAhahahaha...)