I would make a movie combining the 2006 and 2007 waves (Which I think were Toa Inika/Piraka and Barraki/Toa Mahri)
The movie would last 2.5 hours long. The 1st hour would basically represent what happened on Voya Nui and the 2nd hour and a half would represent what happened underwater. Sometime during the movie there would be flashbacks explaining what happened to certain stuff (ie the Piraka fighting the Toa Nuva, how the matoran like Jaller become Toa Inika and how the Toa Inika became the Toa Mahri and what happened to Dekar)
The main protagonists will be the Toa (duh) and the main villian will be the Piraka, Barraki, and Maxillos (the guy Makuta possessed in the 2007 wave I think)
There will also be an end credit scene like in the Marvel Cinematic Universe showing off Mutran doing an experiment on a matoran (which will become Vican) and like a 20 second scene showing off the Toa Phantoka and Mistika.