Personally, I'd like to see the origin story start off with a mix of the MYP origin and She-Ra's origin. Depending on how well the movie would produce revenue (which we all know it can) Mattel could go the passe trilogy route and do a spin-off series for She-Ra just like Marvel's doing with X-Men and Wolverine. The only thing I would change with the story that I don't think any production has done is Adam knowing that his sister was kidnapped by Hordak. Having Hordak kidnap Adora and leaving Skeletor/Keldor to fend for himself against Randor and the Defenders in the first twenty minutes or so of the film could definitely generate intrest for casual moviegoers as well as the hardcore fans. It's just my opinion an opening like that going into the Adam becoming He-Man origin could solidify MOTU's future as far as Hollywood is concerned.
Besides, you know Hollywood will put its stamp on the movie and take liberties that aren't going to set right with everyone. This route ensures everyone gets what they want: the film's producers, Mattel and everyone involved gets paid royally for recycling a franchise and the fans can have their cake and eat it too by getting a richer story as well as the potential to see more of their favorite characters protrayed by live actors.