"Replace face" requires that the surface being used extend past the edges of the face being replaced, which can make it difficult to control the edges of the resulting object. "Split body" has the option of extending the boundaries of the splitting surface. I would like an option to have "replace face" behave this way also. That way, a surface with a boundary that is very close to the same shape as the face being replaced would work without having to pull the edges out a little extra to make sure they extend past the the edges of the face.
