Hmm, my input is;
Apple Cider - As close to the real deal as you can get, something like the hot apple cider you can get at Tims. The vaping world is lacking this flavour.
Caramel Apple Tobacco - I've mixed these three of your juices together and people love the smell, one of my friends in Deep River started to do it too actually and we both agree it would be a hit.
Sour Green Apple - Like the goopy green slime that comes in the tube, the one that makes your face almost cave in.
Grapple - A grape/ apple flavour that I have also mixed using your juices that turned out good. Grapples actually exist but are merely apples injected with grape juice.
Cookie Dough - I mean c'mon who doesn't like cookie dough
Cranberry - Not a popular idea but I love cranberries and have to put it out there. Cranberry on it's own or mixed with Raspberry, pear or grape would be awesome IMO
Strawberry Rhubarb Pie - You never know... Could be good. I know the pie is.
English Toffee - Again like what you can get at Tims
Smore - Exactly as it sounds and I bet would also be to die for.
Butter Tart - Not sure if this could even work but it would be epic if it can be pulled off.
I have other ideas that are more outlandish, like a Pizza Juice that tastes like the Pringles and so forth but I'll keep them to myself lmfao.