I know what you mean about the sweetness of Tanariva and I think that using it as a base for something with a salty/nutty inclusion is a fabulous idea. Try something weird, maybe a roasted/salted sunflower seed butter studded with roasted sunflower seeds (unsalted) and sprinkled with a smoked coarse salt. You could also consider mixing the butter with the melted chocolate to make a spread. Sun-duja!
Another thing that occurred to me would be to use the Tanariva as milk in a "dark milk" blend chocolate. You don't want to use something really fruity like Manjari, but using it to lighten up Coeur de Guanaja (or even regular Guanaja) could be really interesting.
And - on a complete other note - try pairing the Tanariva with Brooklyn Brewery's Pennant Pale Ale. Classic English pale ale malty/yeasty/bready - served temps in the 50s, not ice cold - goes extremely well with the Tanariva. I did this for a pairing event last holidays (2011, not 2012) and it was the dark-horse hit of the pairings.
clay - http://www.thechocolatelife.com/clay/