Backlog Marker for Minimum Marketable Feature Set

I would like to be able to mark a "red line" just below the Minimum Marketable Feature set (MMF), in the "plan" tab of Greenhopper (Rapidboard version(s), not the classic one).

While I do communicate to the team what these are, it would be good for them to be able to see where it is without having to ask.

I think it would make sense to place the "red line" in the left-hand Epic column, and be able to drag it around, just like Epics.

Many thanks for any consideration!