I also am a fan of "fortification" occasionally, particularly when you have very sweet ciders or meads that "stick". I had a braggot (imperial stout style) that stuck very sweet, but after fortifying it with bourbon and bottling it still it was one of my more happy accidents, a very unique flavor. I'm about to try blending a cyser that stuck recently with bourbon as well, the vanilla and caramel of bourbon should blend nicely with a sweet apple wine. Now, it would be that much better with calvados but my wallet disagrees!
(Aside note...If you want a tasty experiment, this one involving no fermentation, at least on your side, you can make a rather tasty "pommeau de normand". I've never had the original, but its a blend of unfermented juice and apple brandy. A bottle of calvados, and a bottle of good apple juice (martinellis is tasty for this purpose), blend 50/50 and rebottle. Makes a nice little aperitif, at about port or sherry strength.)
I too have fermented somewhat bland and uninteresting ciders on occasion. I admit, I like mixing them; most of my attempts to add flavors before fermentation or bottling/kegging either fail or fall short in some way but a slug of Ribena or a bit of cranberry juice in a glass of otherwise somewhat bland cider is not bad.