Unless some 377/3s suddenly become available, then 10-car 377 formations can work to Tunbridge Wells, as they do with Networkers. Freeing those up from the Coastway and sending them to Southeastern seems to have its merits.SE will need at least 15 more 377s to make that happen, and for 12-car 377s to be permitted on these services. In theory this is doable, but how many SE get depends on how much of a net gain Southern need.
What net gain can we identify Southern needing?