I would like to assign target dates/deadlines to feature stories, not just release markers

It would be great if you could assign a target date or deadline to a feature story, not just to a release marker. We have stories which have drop-dead due dates - they must be completed by a certain time. Ideally, if a story with a deadline is too far down in the backlog, it should turn red, which means you need to move it up in the backlog so that it gets done in time. It's not sufficient to just move this story above a release marker (which has an associated date), as we have a lot of stories each with different due dates - it seems silly to add in a bunch of release markers just to associate a different due dates with particular stories. Can this be done? It seems like it would be easy to do, as you guys already have due dates for release markers.