In a lot of ways, you prefer the battery weight to be in the wings. The main one is that it reduces the load on the critical wing-fuselage junction (the source of zero-fuel-weight limitations in larger aircraft).
You can package things however you want, even in weird shapes. Not "has to allow liquid to flow downhill, even in rate 2 turn". I'll bet there's still wins to be found even with putting batteries in wings.
