“That the cause and effect is flipped — and the expanding universe is producing the force and not the other way around?”
Perhaps. I have a similar hypothesis, but about gravity, which I see as kind of the flip side of this force of expansion. I believe gravity is simply an effect of drag caused by the interaction of the expansion force and the inertia of the matter that the expanding space is trying to pull along with it. Spacetime is free to expand where there is no matter, but when matter is present, its inertia resists the expansion, causing spacetime to distort when it tries to pull the matter with it, and this distortion in the geometry of spacetime causes the gravitational effects we are familiar with.
Wow. Very interesting idea!
So there is a larger all encompassing force (super negative gravity) and gravity is simply an artifact of that force. That would explain why it repels versus attracts.
Cool.
Have you tried to prove this mathematically?