It looks like a good idea, it just needs a bigger budget and some minor reworking to play up it's awesomeness. I mean, Ferdinand Magellan was a dude so awesome that they named an entire Strait after him. Having him thrown into a post-apocalyptic future where waring tribes fight for control of the wasteland while aliens secretly administrate the ruined world has to be awesome, as well.
What they should do is tone down the space combat, give Magellan a pair of flintlock rifles (with sword bayonets) that shoot huge giant-robot killing laser-beams, add some giant robots, replace the space fighters with giant robots that have realistic zero-g movement, have the alien mothership actually be the moon( yeah, the whole moon), and then you've got some awesome.