Currently, to speed up an Action Strip to double the speed, you scale it by x0.5 on the timeline, to make it half the speed, you scale it x2.
But what if you want an Action Strip to start at double speed then, by the end of the Action Strip it has now slowed to x1 speed, with a smooth graduation between? Some kind of curve would be needed, and of course it would need to visually represent on the timeline properly so that one could time other animation events could happen at salient moments of it.
Is this possible? Has anyone done it? If so is it a plug in?