I think I posted about this movie, I had mixed thoughts about it... there were sequences I liked (the "Avatar" sequence, the Enterprise-esque opening sequence which works better when there aren't names all over the place, the Big Market, etc) but the issue I had with it wasn't the cast, it's that they were playing characters.

There's a moment early on where Laureline does this little greeting hand wave (which I have since taught myself), and I love that.  And watching the bonus features of that moment where they're playing around and the goofiness they had on set, I'd rather have seen THAT movie.  I don't want to see Valerian and Laureline, I want to see Dane DeHaan and Cara Delivigne.  I want to see two Eurotrash club kids save the universe, THAT'S fun, that's more in the vein of The Fifth Element which is what we were all hoping this movie would be.  They were waayyyy too serious in the flick.

I think having them just be them would have fixed a lot of problems.  Don't get why Valerian is into Laureline... but if she was Cara D, yeah I could see that.  Presuming that the long list of women he had been with before were officers and so on, a funky stoner would be different for him, AND push him out of his comfort zone.

Alex (the ship, remember the ship had a name) felt more like a third person on the team but not quite enough, there wasn't enough personality in the ship or what it did.  Obviously it's close to the Millennium Falcon because the Falcon ripped it off, but where was the funky French weirdness?

You know what movie could have been a good model for this?  Ghostbusters.  Have these two (three?) be the funny ones but it's a serious world and everything is serious and has weight, but they're kinda just going through it having fun.