If I could ask for anything, I would probably be very specific (lol). Ex: Manor chum X Dapple Dandy pluot.
Manor: very cold hardy, taste=not too bad, somewhat resistant to black knot, ripens eary (for short seasons), bush form
Dapple Dandy: not cold hardy enough, BUT super delicious and ripens early too, tree form
My idea of the seedling:
Small tree, good fruit, perfect for northern regions and disease resistant!