This is A GREAT idea !
Actually I was thinking something similar, in order to have non-linear crescendos. Thanks a lot for posting this request !
I want to go a little bit further and submit the ability to apply curves on different CC controllers. For example in Hollywood Strings (East West) we have the ability to control the loudness of the sound with CC11 and the amount of vibrato with the CC1, so being able to control these 2 different parameters on different curves would be useful. Even if I don't use CC7 very often, the same idea goes for controlling independently the loudness (usually with CC1) and the volume (CC7) with different curves to have even more control of the sound for the instrument.
GREAT request, I am happy to know that I am not the only one who wants to see this feature in the next Notion 6 ! :)
I wish you the best !