I think a cinnamon based one is a must for sure - I'm leaning towards a cinnamon roll type flavor at first because that seems like everyone loves those.I'd like to see both a WPI/Micellar Casein blend and a fruit juice like isolate. For the blend, I'd really hope for a banana flavor, something cinnamon based (horchata would be great) a coconut flavor (coconut cream pie, toasted coconut, coconut ice cream). Maybe down the road a lemon cream pie or lemon meringue, root beer float, and some holiday flavors like eggnog and pumpkin pie.
I used to buy 4Ever Fit whey isolate fruit flavors. It was like drinking Snapple instead of a milky or creamy fruit flavored shake. I'd try something like that for sure.
I like banana flavor myself and had thought about a banana split flavor. I love chocolate banana and peanut butter banana flavors myself too.
I hope that we can grow this to be able to do some fun holiday flavors - I love eggnog myself. I would love to be able to do like a peppermint mocha seasonal flavor.
I never tried 4ever Fit's fruit isolate flavors. You mentioned it being like drinking a snapple, that made me think of another flavor I'd like to do in a clear/fruit flavored protein and that would be an Iced Tea flavor. We had a sample of a tea flavor for the upcoming EAA product and it was incredible - I could drink it all day long and that's what made me think it could be an awesome protein flavor and be refreshing and enjoyable to drink.
You mentioned coconut - I thought about trying to do something similar to the Samoas cookies.