If M64 showed a blueshift, what unlikely scenario would this imply about local gravitational forces?

Local gravity overcame universal expansion over tens of millions of light-years.

A blueshift in a galaxy as distant as Messier 64—estimated to be tens of millions of light-years away—would signal that the object is moving toward the observer. For a galaxy outside the immediate gravitational vicinity of the Milky Way's Local Group, observing a blueshift would imply that the local gravitational attraction exerted by our cluster of galaxies is powerful enough to completely overcome the persistent, large-scale stretching effect of the expanding universe. Because the expansion effect dominates at these great distances for objects not gravitationally bound locally, observing a blueshift for M64 would represent an extremely unlikely physical scenario contradicting established cosmological models.