I struggle to see happening, but SE London is certainly unloved...
Sort out ticket barriers, deep clean the stations, have more staff around, brighten the fleet up, improve Sunday timetables.
It would be nice to see the station buildings opened up - far too much of it is boarded up. Catford Bridge would be great for a cafe/shop (a bit of rental income for the railway) and a waiting room. Same for Shortlands and many others.
SE doesn't try very hard with revenue at all. Forgetting ticket barriers, just more ticket machines at stations like Lower Sydenham would be useful; one for the entire station is rather poor. Same for Penge East - two machines on the London side (with a ticket office), but nothing on the country side. When I need to travel towards Kent, I need to walk over the footbridge bridge twice. If we're serious about accessibility, I should never have to climb stairs at a station with step free entrances just to pay for a ticket. If you're disabled, the other option at both stations is a 10-15 min walk around. Madness.
If the Abbey Wood example was repeated, any operator would surely gain not-so-insignificant amounts to fund station improvements. Brixton is certainly busier than the 1.1m entries/exits claimed. Catford Bridge is 2.7m and Greenwich claims 3.7m. None of these have barriers - lots of revenue potential, and that's without the housing developments all over SE London.