Based on what I remember of the book, Mistborn-the-movie could be boiled down into three things.

1) Kelsier and his gang. As I recall, this consisted in large part of Kelsier doing mysterious things off-screen, and his gang (in large part) doing nothing while they waited. They did some talking, planning, and training, but nothing of import. Nothing that would interest a film audience.

2) Allomancy. Allomantic fights were relatively interesting to read, but wouldn't look very good on screen. They consist of standard hand-to-hand combat (enhanced by burning metals, but still basically looking like fist fights), throwing coins, and zooming around by pulling and pushing on the environment. For the life of me I can't think of how to make throwing coins cool-lookin'. The flying could provide an interesting dimension, but stuff like that inevitably looks awful on screen. Wires are obvious and slow, CGI is corny and unrealistic. I just don't think Allomancy could be done well.

3) The Lord Ruler (specifically, confrontations with him). Besides Kelsier and Allomancy, the lord ruler is the only unusual or interesting part of the book. However, he's off-screen for 99% of the book. His initial entrance is preceded by a neat battle, which would, as I said in the last thing, be hard to do well. The final confrontation is little more than getting cornered and grabbed, and then tearing off a bracelet or something.

Anyway. . .I dunno. You could maybe take the world and create something interesting, but based even roughly on the books you'd get crap. A terrible rebellion-plot, unrealistic and unimpressive magical battles, and an enemy who does almost nothing at all.

I'll probably watch it if it's made, but I can't imagine it being anything special.