1. Not really actually. Marsden couldn't even really have a schedule with Superman Returns. "More" really wasn't possible. I don't think alot of people understand movies go farther than just the script. There is alot of studio politics, contracts, schedules, etc. It isn't easy as "writing him" a certain way. Keep in mind they didn't actually SHOW Scott being killed and I think this was done purposely so he could easily be brought back in the future if they wanted.
2. Blame Singer for Rogue. He is the one that made her into the damsel in the distress and planted the character seed for her.
3. Jean dies?? Uhhh sounds alot like the comics. And in the comics she came back. Hmmm. Let me tell you how she died she could be brought back if need be.
4. That Xavier scene was done by Ratner I believe. I do know it wasn't even put down on paper but not sure who actually thought it up. And ONCE again...things like it happen ALL the time in the comics. It is like they tried to make this film closer to the source material and please more fans but there is alot of people that didn't like it.

Oh well...to each his own.