Understood. Although some of them don’t have a choice to go anywhere but Victoria as it is their only London Terminal. What about those heading to Woking, Southampton, Watford, Gatwick, Brighton, Croydon, Reading, Staines?
Gatwick - Into Vic and then Gatwick Express or from Kent, its a relatively short trip round the 25. Gatwick also has other options from London Bridge or even High speed up to Pancras and then down to Gatwick.
Croydon - If your anywhere on the Vic line then Beckenham Junction and then Trap is a fantastic option. Its only a 23min trip from Beck Junction to East Croydon.
Reading - Crossrail will open up going though London. Not sure how well it would link the Kent Coast to that side of London but its an Opportunity for sure.
Generally I hate going in and then back out but the railway was built a thousand years ago and everything goes in/out by design. As @Horizon22 points out. Southeastern is very fortunate with their links into London. However, coming up from the coast becomes more prohibitive. Gillingham to Charing Cross for example.......