The problem with
@rdlover777 suggestion is many of the Ashford to Ramsgate stations have short platforms, Wye, Chilham, Chartham and Sturry have 4 car platforms, Canterbury West has an 8 car platform and when the train stops at all but Chilham they sit over their respective level crossings (cause huge road delays), I know that 12 car 395s are required but the infrastructure will need to match it!
The 465/466s need a complete refurb yes, improved door yes, end walkways to help with passenger flow, yes and 25 years taken of their age (um were buggered there ditch em start again)
As it is the Hastings to Charing Cross service via Tunbridge Wells is hugely unreliable, whilst I accept adding better connections to Eastbourne or Brighton would be beneficial but by adding coastline work as well risks more unreliable services that are already pretty long already!
And as it recall Maidstone West was about to lose its HS1 services already they are never going to run them further down the Medway Valley to Tonbridge, maybe the proposed Marsh Link line being doubled electrified and 395s running to Eastbourne would appease your want for SE services to Eastbourne