Well if they had adopted the Direct Northern Railway proposal of 1844, the "ECML" would have run via Peterborough, Lincoln & Gainsborough., whilst the Eastern Counties Railway wanted to run from Wisbech to Lincoln & Doncaster. (David & Charles Regional History, East Midlands).
So , Retford, Newark & Grantham may never have developed to much more than large villages, very small towns and might have lost any stations in the Marples-Beeching era. Or, at most, they would be relatively minor stations on the Sheffield - Gainsborough/Lincoln, and Nottingham - Lincoln lines The Nottingham - Grantham line may never have been built, but Nottingham - Melton Mowbray - Stamford - Peterborough might have remained open as an important cross country route.