Graintable rack extension
Something like Maelstrom but allows me to load and process any sample into it. I see this as being a sampling device as well, so it should have the sample button (even though processing grain-tables could take a long time after the sample is recorded).
Additional, the ability to trigger envelopes on grains would be an excellent creative tool. As would the ability to sync LFOs to grain coarseness. Naturally, the modulation matrix that Thor and Parsec have would go a long way to making this flexible enough to warrant a $100 price tag.