Giant doll bodies, you say? :D
I'm excited to see your new artwork!!
So I did a little google about sewing curve in pants because I thought like you that maybe it's darts that would work?, and I found this whole list of resources about getting pants to fit when you are sewing: https://curvysewingcollective.com/pantsmaking-resources-fitting-and-construction/ ...so maybe something on there will help? I haven't checked them all out yet.