Jewel drop combos can be set up to go as high 6x and 7x. More than the 4x and 5x combo that gives a dragon token boost and diamond boost respectively. They do also occur by chance when cascading. Maybe a summon for one and an ascension item for the other, in addition to the diamond boost.
Sorry not clear on what you’re requesting here…?
Are you asking that additional ascention/ crafting material rolls be awarded for high combos?
Crafting & mat rolls are pretty well fixed per province & stage so I’m not sure how/ if this would be implemented.