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What sound are you after?
The Erica Synths fusion flanger is kinde big for your setup but it sounds lovely!
A Serge ResEQ could be fun. Or maybe even a QPAS. A filter in general would be nice.
Another good idea would be a 2hp dual sample and hold. If you put audio into the main input and then trigger it at audio rate as well, you get a simple but cool voltage controlled downsampled/"bitcrush" effect (in stereo if you use both).
I'm a fan of the Nautilus, for delay and effects: