There is already a service from Ashford International that calls at Bearsted, Maidstone East, Barming, East Malling, West Malling, Borough Green & Wrotham, Kemsing, Otford, Bromley South and London Victoria.
Now, if you could turn that into an all-stations train you could swap the stops off the service that comes from Canterbury West (Charing, Lenham, Harrietsham and Hollingbourne).
In order to remove the calls at West Malling, Borough Green & Wrotham and Otford you'd need to find some way to provide them with a replacement that's semi-fast. Good luck with that.
But then you might be able to achieve, from Canterbury West:
Chartham, Chilham, Wye, Ashford International, Bearsted, Maidstone East, (Swanley), Bromley South, London Victoria.
The challenge would be, would such a service be full? And could it be pathed effectively without catching up to the train ahead?