I'm not sure what alterations to ask for, but I'm considering one of the following two routes:
I think that both routes would improve fit, it just depends how gradually you want to move to a better fit. If there are a lot of potential alterations, I would suggest getting a part of trial pants as a way of improving the fit without having to spend for a nicer fabric and then not be completely satisfied with the results.
In regards to your comments. I don't think that decreasing the hip measurement would affect the issue with the "wedgie" since that measurement is taken higher than the seat. It may make the pants a little tighter across the rear, though (different that the wedgie issue).
Increasing the back rise at the seam will go a long way to fix the "wedgie", but you should probably also reduce the inseam by 0.25. This will make the very bottom of the crotch seam (where front and back rise meet) sit a little lower (it won't affect the overall length of the pants as long as the outseam remains the same). Scooping out the seat help mainly with getting rid of any loose fabric behind the thighs (just below the buttocks). That doesn't seem to be that big of a problem in your case so 0.25" might be enough.