I still think the duplication is removed by not having Southeastern run east of Abbey Wood (on that branch) - and east of Dartford overall.
Everything east of Abbey Wood is taken over, and improved by Crossrail, with various termini along the North Kent route.
That's pretty much what I thought with 4tph terminating at Dartford, 4tph at Gravesend, 2tph at Rainham and 2tph at Maidstone West?