When composing it can be very convenient to have the ability to display a background sequence (in grey). For example you can have your chord progression in the background and you layer bass or lead on it.
It already exists in seq24 where you have a dropdown box to select your background sequence of choice. In qtractor that dropdown box could lists the clips.
Here is a use case : http://www.midichords.com/posts/arpeggiate-your-chord-progression-and-create-a-lead-melody
And a screenshot on the seq24 way to implement it.
Do you think it would be hard to implement in Qtractor ?