I think Marvel is wrong to force all these bloody origin stories on the public first. There's no reason why they couldn't just go straight to an Avengers movie, and spin-off characters later if they catch on with moviegoers. It worked just fine for X-Men (and Wolverine).
The problem with origin stories is that they're all old as the hills, and everyone can see where they are going miles away 'cause all the movies have the same cookie-cutter approach. Also, origin stories are by no means the best or most memorable stories featuring that character, in most cases. If you look at something like Giant-Sized X-Men #1, the origins for the likes of Storm, Nightcrawler and Wolverine are about a page each. If you need to do it, do it like that and get on with telling a real story. It may not make it to a trilogy so you can tell the cooler stories you have in mind!