That was a first pick a while back, mostly because I couldn't figure out how to fit in Thor's granddaughters since the eldest even wears Ronda's fight gear. Then as I was putting together that last post the idea struck me like a bolt of lightning.
The idea that struck me...
Movie starts on a silent barren landscape, camera is near to the ground the low whistling of the wind is all we hear. Text appears at the bottom of the screen: Midgard 3025 (or some other future time). Suddenly armored boots walk across the frame as we pull back we see the Girls of Thunder are trekking across the countryside.
Landscape looks as such but sans Galactus and King Thor since he'll pop up in a sec.
As they walk we see farming equipment that Thor has put together over the years as he tills the soil trying to bring Earth back.
Youngest: Are we sure grandpa is here?
Middle: Mother saw him heading to the Bifrost with the book again. Just wants to make sure he's ok.
Eldest: There he is.
We see King Thor sitting atop a rocky outcropping with Mjolnir at his feet as he reads through a large ancient book, the lock and chains that kept the book sealed rests on top of Mjolnir.
Using the 'Unworthy' book as an example
The girls approach Thor and make small talk as he reads on. One of them asks what he is reading.
Thor: Looking to see if there was something I missed, something I could have done to change this.
Eldest: I don't think anyone could have stopped this from happening to Midgard.
Thor: Not the event but if I could have stopped it at the source then they could have been saved. There must have been something...*he looks up from the book* Maybe you will see what I could not.
We pull in over Thor's shoulder as he goes back to the cover: RAGNAROK, big music swell as the words rise up from the cover.
Smash cut to Thor picking up from Age of Ultron. They started Thor 2 with a look far in the past so I thought starting Thor 3 with a look far into the future would work.
Maybe for a post credits scene we get King Thor closing the book but before he can say anything we get the return of the being that destroyed Earth. Could be Kang, Beyonder, fuck if I know but this person would be the next big Avengers villain. The main story of Ragnarok would be the final set up to Infinity War and this scene would allow people to figure out who this next villain is for his arrival in present day during the post credit for Infinity War. Hopefully this will lead to less: Who is [Thanos, Apocalypse, etc] that happens in the theater at the end of each movie. Grant it they even named that next movie Apocalyse and no one knew who he was due to being a blue kid.