I don't know about trying to tell the whole story of voyager in one movie. I just don't think it would work. There are basically three possibilities.
AU prequel, like nutrek. They do the starting off thing, but its in a different universe so it is different.
A long episode. The movie takes place during the seven years they are lost, and its like the two part episodes, only more movie-ish.
An after movie. It takes place after they get home, and probably something happens and the universe conspires to bring the crew back together to save the day.
Personally, I like the first. It would be cool to see how it woul work with different interpretations of the same characters