Custom fields per list

Currently, custom fields can be added globally through Newsletter Settings -> Subscribers -> Custom Fields, and they apply to all lists. But it would be great if this capability could be refined to have custom fields per list only. Our use-case is that we have different lists for different uses, and currently custom fields apply across all lists which makes data handling a bit troublesome. It would be more neat and effective if custom fields could apply specifically to a list only. 😉