It can work, but you do need intense flavors. And as Jim D mentioned, Valrhona Opalys is very good and probably the least sweet white chocolate out there. Recently to save a few $$ I bought a bag of Callebaut Zephyr instead (Zephyr was only $7/# instead of $12!). It's a little more opaque and less sweet than a lot of white chocolates but not to the extreme of the Opalys. It's 34% cocoa butter, so I think that helps.
You do want to concentrate your flavors to stand up to the sweetness. I make a passion fruit white chocolate ganache using Perfect Puree - their passion fruit flavor is already concentrated. And today I made an orange caramel ganache using white chocolate for which I infused the caramel with orange zest, then added reduced orange and tangerine juice and a little cointreau. I think that is what Kerry means by layers of flavor - not necessarily making different layers of fillings, but using different forms of the same flavor. Both of those ganaches go in a 60% dark shell.
Also, I would have to disagree with the "people love white chocolate" idea. I mean, I know a few, but I almost always combine white chocolate with dark so the whole experience is not too sweet. I only have one regular item that is all white chocolate, and even that is Valrhona's Dulcey "blond" chocolate, and I add salt to it.
