Re: Storm VS Mystique
I'm pretty sure Lawrence will receive the highest billing of all the female actors. But billing order has no real effect on who has the most development or screentime. Patrick Stewart was first billed in both X1 and X2 even though Wolverine is the clear protagonist in both films. Billing order is often just a contractual stipulation.
I believe the final billing order will be almost exactly as the "photo wall" Bryan tweeted a couple months ago: Hugh Jackman credited first, Jennifer Lawrence, then all the stars of FC and the Original trilogy, with Anna Paquin receiving the prestige "...and Anna Paquin" credit and then minor characters/stars credited after her (and probably not included in the opening credit roll). I would be willing to bet money on this if anyone is interested...