Firstly how long will the movie be? Eh idk. It can really depend. Probably at minimum 1 hour 30 minutes and at maximum 2 hour 15 (excluding both intro and end credits)

Who are the Kerbonauts? Easy picks. Jebediah, Bill, Bob, Valentina and one Unnamed Female Kerbal (Yall get to choose the name). They'll all be a bit different because having the same faces would be kinda boring. Same with everyone else that will be seen in the movie. They'll all look different from each other.

For the acts I can imagine it being so that

1st act: The planning and then training the crew while the Mission is being prepared like launching the Transfer stage parts into Kerbin Orbit and the lander being sent to Duna before the crew. And at the end is the crew launch sequence. Which will be heavily inspired by Apollo 13's (1995) liftoff scene with a similar (-ish) soundtrack. And it ends with them docking to the Transfer stage

2nd act: They start their journey to Duna. Nothing much happens except some minor Kraken attacks and some alarms going off and the crew needing to fix stuff. And at the end they get to Duna Orbit and the crewed craft undocks and Rendezvous with the lander on Duna orbit

3rd act: They land on Duna. And then they explore and find some mysterious stuff on the surface. And They'll stay there for 240 days. And at the end (where the ending soundtrack [Askerad "Home"] starts playing) they return back home. Where they return as heroes I guess

So yeah. Oh and Valentina will be Russian and the Granddaughter of Valentina Tereshkova. Because why not? If yall vibe with it then I'll include this detail in the movie

And maybe a bit of a romantic interests between Jebediah and Valentina or something like that. If yall Vibe with that idea