Ability to reset 'progress' for release burndown charts

I really like the idea of having a release progress burndown chart, however we haven't been able to use it successfully. One major challenge is that as features get added/removed the scale can jump up and down wildly. I would like the ability to either 'reset' the baseline manually, or only have the baseline begin when the release moves to an 'in progress' status (and reset if you move it to not started and then back to in progress).