When doing planning we use themes to track the different types of work we are doing. To do this we have co-opted epics to display and filter on this information easily. This means that we can no longer easily use epics for their original purpose of decomposing large stories.

My suggestion would be to add an additional panel, similar to Version and Epics for adding and sorting into Themes.

The other possible solution for this is to allow placing a story into more than one epic. This way a story could be part of it's correct Theme and traditional definition of Epic.