I reckon the following ECS moves from Stansted Airport could definitely be converted to useful passenger services:
On Mondays:
Real-time train running information for 5B10 0445 departure from Stansted Airport to London Liverpool Street on 17/07/2023. From Realtime Trains, an independent source of train running info for Great Britain.
www.realtimetrains.co.uk
On Fridays:
Real-time train running information for 5B10 0445 departure from Stansted Airport to London Liverpool Street on 21/07/2023. From Realtime Trains, an independent source of train running info for Great Britain.
www.realtimetrains.co.uk
On Saturdays:
Real-time train running information for 5B12 0440 departure from Stansted Airport to London Liverpool Street on 22/07/2023. From Realtime Trains, an independent source of train running info for Great Britain.
www.realtimetrains.co.uk
These are all formed from 1B98 the 0340 Liverpool Street non-stop to Stansted service that only runs on Monday, Friday and Saturday mornings. Based off of my observations of clueless tourists heading down to the station at 3am when there's at least 2 hours till the first train, there would certainly be some user base, as there are some very early/late arrivals of planes, not to mention planes that arrive 2-3 hours late, as mine did recently, as well as airport staff/cleaners clocking off from shifts, for whom a 0440/0445 service from Stansted on the applicable nights would be useful.
Such a service would likely run nonstop due to station staffing hours, at intermediate stations, although on a Cheshunt stop could possibly be made, given it stops there for pathing anyway (Mondays & Fridays), and the first northbound would have departed from Cheshunt by then. This would then form a useful connection into the first southbound London Overground service via Seven sisters.
I am aware that Stansted does have 24/7 coaches into London operated by national express but many tourists and passengers prefer to use the train, and at least to Liverpool street the train is faster on journey times than the equivalent coach. Either way it seems like a bit of missed opportunity from Greater Anglia, especially given that Gatwick and Luton have 24hr overnight services on all or most nights of the week.