Share custom attributes without sharing WorkFlow?

By using Work Item Type Category, we can share workFlow and custom attributes among different Work Item types.

The user is asking us to be able to create a different workflow for each WI type that so far were all sharing the same WI type Category.

If we need to link every WI type to its specific workflow, we will have to create a different WI type Category for each WI type, and thus our custom attributes shared among all WI types will have to be added one by one to each individual WI type Category.

I would really appreciate if some one has any idea about how to share custom attributes among different WI type Categories.
A solution could be the ability to link a different workflow to every single WI type within the same Category, but this is not possible, isnt?

thanks in advance