I think we can easily have multiple different reference spaces in one PlotArea using the Scene's world affine transform's scale, i.e. Scene.world.scale. Would be the way we do things like matplotlib's twinx functionality, but we can do it much more elegantly.

Also automatic linking with selectors to update the axes. Allow update the "reference space" ranges dynamically using a selector. For example, to show a zoomed in range of a large range in another subplot, update the axes dymically.