And indeed it is. Actually, I think @phinds understands very well what you are suggesting. The problem is that it has implications that don't match observations. Namely if the universe was a sphere, redshifts would not be uniform and would point toward its center. In addition, the density of galaxies would decreade with increasing distance from the center. So it isn't that he doesn't want to try to understand your scenario, it's that he already has (A lot of people ask similar questions) and we already know that it conflicts with what is observed. ....you've also mixed together gravitational and cosmological redshift in an odd way. That one's new.