@Rex
There seem to be two problems with the Fullscreen cached images
1 - The disk size required to store them (not a problem for me, but I have seen complaints about it)
2 - The fact that they clutter up the scenes directory
The first can be handled as you suggest by making the caching optional
The second can be handled by storing them in a different directory rather than in the scenes directory itself. Instead of appending a suffix to the .scn filename you append a prefix specifying a directory at the same level as the scenes directory - .e.g. instead of storing the cached image in data/scenes it is stored in data/scenescache.
Please note that currently I have over 4000 scenes installed plus a few thousand I keep elsewhere to prevent overwhelming the system. At point I had over 40000, though that was a temporary situation where I autogenerated a large number of scenes to allow me to explore how the various movement types interracted. The main reason why there are a large number of scenes, at least in my case, is that when you want to have several scenes that differ only by changes in a few parameters it is necessary to have a scene file for each combination of parameters.