While we’re waiting for modular FX routing, check this out: http://www.quantum-fx.com/
It’s a plugin that includes a modular editor (akin to Reaktor) with widgets for creating FX, or stringing together already created ones. You then save your effect, load it up in your Renoise effects chain as a VST, and open up your custom effect.
Pretty cool, but not easily automated (the envelope parameters come up very strange)
Peace,