XXD17
Draco rex
The problem isn't Grass/Flying itself, the problem is is that it's terribly predictable.
And seeing as Empoleon and Blaziken are birds and not Flying-Type, I have hope for 7Birb. Granted, owls are capable of fully fledged flight unlike penguins and chickens, but Delibird, another penguin, was Flying-Type and capable of flight, so a flightless bird can have Flying, so maybe a flight-able bird can skip the Flying.
That's not completely true. Delibird can be also partially based on a tufted puffin, which can indeed fly: http://www.tringa.org/images/1724_Tufted_Puffin_06-25-2011_3.jpg . The only one that really came out of left field with the flying type is the doduo line, but I have a theory on why that may be the case: https://optimalotaku.com/xiaoperiors-pokemon-corner-thoughtful-thursday-flys-dilemma/. The only real way I can see this working is if it's based on a burrowing owl or something...