But unless you are capable to change the physical dimensions of the plane in mid flight the only thing you have to play with is the CoG and as soon as you bank you do not escape from the fact that gravity will have an influence in balancing all horizontal forces whatever the reference point you will use.
Ah, here I think we have the crux of the matter. Gravity is always acting solely in the vertical. It will never be a factor when considering
horizontal forces, whether you are level, in knife-edge flight or anywhere in between. As was stated before, the horizontal plane is per definition perpendicular to the gravitational force so there will never be any component of weight (gravity times mass applied at the CoG) in the horizontal.
If you consider
lateral forces in the aircraft reference system, however, you will see a component of weight projected on the aircraft xy plane when you are in a bank or pitched up/down. That is why I have taken great care to be working in the horizontal plane rather than the aircraft lateral plane in this discussion.
Regards,
Fred