don't update the cache in the background while in isolated mode, and reset it only when you start play while you are in isolated mode
This way you can work in isolation mode,and keep your cache.
On playback it will create new cache based ONLY on the isolated mode.
Question should this also work the same when you leave isolation mode? Will it retain the cache of isolated layer ,and only reset the cache of the isolated layer when you start playback in the normal mode?
I'm not sure about what would be better,might need testing,that last bit.