Temporarily freeze/rasterize layers into image sequences

It would be extremely handy with the ability to temporarily freeze/bounce layers/encapsules into rasterized image sequences in order to save computational time when working on other layers. This way you could work on much heavier projects than your setup normally would be able to handle.
I’m for example at the moment trying out rotoscoping with complex gradient layers and with Synfigs capabilities the results are potentially stunning but the project is rapidly getting out of hand. The computational time is increasing exponentially for every layer I add and I can’t really get a feel for the animation since it’s already producing one image/second and pretty soon it will become impossible to work with.
Now, I could manually render these layers and import them by hand but this would take a lot of time and will have to be done repeatedly all throughout the project… this would instead potentially seem as a very natural, possible part of a fluid and intuitive Synfig workflow.