Just because a wine has been sorbated doesn't mean that it will never ferment again. There needs to be sufficient sorbate in the wine for the volume. So what would happen if you added 1 part of your sorbated wine to 2 (or 3 or 4) parts of currently fermenting similar wine? This may qualify as "a lot of blending wine", but hopefully it would ferment out some of the sugars.
Unfortunately, I have no idea if this will actually work, so could be throwing good money after bad.
Steve
I am kind of thinking out loud, here...
One could try this after blending, as long as sorbate is not added to the other batch. However, it still would have some affect. Even a little would do its number on the yeast with which it comes into contact. Sorbate is not like free SO2, which gets bound up. The sorbate will always be there, even though in a smaller relative amount. Maybe I am wrong, "just" maybe it does actually get absorbed by the yeast, but I can't really say. IBGOWIN might could tell us for sure.
Maybe make a yeast starter with 5 or 6 packets of yeast; Just guessing, I would give it less than a 50/50 chance, perhaps.
And again, even if the yeast don't multiply, maybe with that amount of packets, it might eventually ferment dry.
Wouldn't cost much to try.