LTN gets the Dart driverless train next year from the station. Think of it as the railway station being the South Terminal at Gatwick and passengers are flying out of the North Terminal. Its the same thing as they have to jump onto a driverless train.
The biggest issue with the Southend rail journey is that is takes so long and seems to stop at every station. I used it once many years ago and seemed to take forever. I am not knocking Southend but the rail link is also its Achilles heel.