One of the problems you face is sugar. Cane sugar is a di-saccharide, which is a double sugar combining fructose and glucose. Natural grape sugar contains both fructose and glucose in almost identical proportions. The acid in the wine will eventually break down the cane sugar, but it will take 4-6 weeks. If you taste the wines with can sugar recently dissolved, the mouthfeel will change and have leave a syrupy feel in the mouth. If you taste it while the sugar is being broken down, for some reason, the nose either disappears or becomes a little funky. After about 8 weeks, it should all be back to normal. This is part of bottle shock, along with exposure to oxygen. I'd suggest seeking out wines that are made from the same grape, but have varying degrees of sweetness and acidity. Regarding Trebbiano, if you can't find a sweet version, you could maybe substitute Vidal, a hybrid with Trebbiano as one of its' parents. Vidal is often made as late harvest and as ice wine.
If you add a quantity of 2 parts sugar to 1 part of the original wine, with a small bit of the acid blend and boil it for about a half hour, it should invert the cane sugar and you would have a syrup that you could blend into the wine at various rates. BTW - the acid blend should be available at any wine making or home brew supply store.
Chico - Hey! This Bottle is empty!
Groucho - That's because it's dry Champagne.