Could the effect of “expanding” gravity (gravitational waves spreading at the speed of light) as it travels through space (and therefore becomes less local) red-shift all EM waves and thus give us the illusion of expanding space? As I understand it, our detection of the expansion of the universe is predicated on the observation of redshifting. The further the light source from us, the more it is redshifted by mass and gravity as it travels to us. As I understand it, in the spacetime framework, this could also be interpreted as slowing time.
This seems like an obvious hypothesis which has surely been debunked but a google search yields no clear answer.