[Zubersoft]

If you use the tap button to set the tempo in the metronome and then you set up the automatic scroller to scroll based on the tapped tempo, in theory this accomplishes what you are describing. There isn't an exact mapping between the tapped tempo and the scroll speed - I just ran through some calculations based on the number of measures that would be scrolled in a given amount of time. 

Obviously what you have described would all be in one place and wouldn't have to be tied to the metronome, so there is still an argument to add it. I just thought I would mention what currently exists. If people would find what you described useful, I can certainly add it to the list.

Thanks,
Mike