Re rhubarb acceptance: Squee! :D I haven't got an opinion on red currants because I've never yet tasted one. I need to remedy this.

I wondered if maybe billberries, as opposed to blueberries, might fly for Viperion? Trying to pin down grey-green ingredients that work in baking is not an easy challenge! XD I'm liking Norakwami's idea, but wondering if there could be something added as a... well... bass note to that combination... Oh, this is tricky!