I do get the idea but it's stupid. We got quick back stories in the first movie that's enough. As someone who knows the comics the origin stuff is boring most of the time.
The first movie wasn't an origin...it was "Wolverine and Rogue's Introduction to the X-Men"...it's the beginning for them, but obviously Xavier, Jean, Storm, and Cyclops, were already quite established. The first movie shed some light on when Magneto and Rogue's powers first manifested, but there's plenty room to show the same for Storm, and Cyclops(and how Xavier created his ruby quartz visor and glasses), and how Xavier first contacted them and how they officially became X-Men. They could show Beast when he was an active member of the team before he went on to become a government diplomat. They could show more of Xavier and Magneto's early teamwork, including how they developed and built Cerebro. They could even delve into Xavier's Underground and possibly the Hellfire Club. Plenty of stories to tell before the first movie.