Changing the filters externally requires an Audiosurf restart and as h3x says, there's a memory leak every time a texture reloads.
It is all theoretically possible with the current set of commands, but you'd be waiting for Audiosurf to quit then restart for the filter change (which it's very slow at) or you'd have a memory leak that would get bigger for each new song (and Audiosurf crashes when you reload the textures more than a certain number of times).
Hoping the memory leak issue at least will be fixed if Dylan is still working on this new engine. (*hint, hint*

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