Pointless. Where would the stations go? Harpenden, St Albans Radlett etc, towns that already have rail links.
It’s bad enough catching the all station stopper to St Pancras that takes 45 minutes but feels like 3 days and gives a taster of what’s it like to catch a train from Stansted of worse still Southend to Liverpool Street.
East West got the Elizabeth Line.
And Luton and Gatwick has got Thamelink, which has direct links to around 20 London station.