There should be no such thing as a terminus station - for example Severn Beach should be extended to Pilning , Scarborough should extend to Whitby, Henley on Thames should be extended to join up at Marlow, and Windsor Central should join to Windsor Riverside. In extremis, all stations at line ends should be loops like Dungeness on the RH&D.
Why?
My original. I fear my sense of humour was too dry - I was joking. though there are some termini that could naturally be joined onwards. Skipton to Colne, Tweedbank to Carlisle, Uckfield to Lewes