Why would TfL want it right now?
SWR suburban branches run at 2tph. There is no spare rolling stock to strengthen services or spare paths to/from Waterloo. TfL are dead skint so there is no money to do up stations. Why would they want to tarnish the London Overground brand?
Using the same points the opposite could be used as an argument for them taking it on.
TfL are skint, so the lack of paths into Waterloo means that there's no infrastructure spend which is needed up front and they can just creaming off the ticket sales.
The cost of station repaints is fairly small in the overall picture and could just be added to the operators list of things to do (again no up front costs for TfL who are skint).
TfL can just point to the fact that they want Crossrail 2 to be built to allow extra services to be run and can then claim that the extra income from the SWT metro services will allow them to get it built sooner. This could be down to that they can stump up more of the money for the building of it from day one.
They could even, where it ties in with other renewals and enhancements even start to build in redundancy for Crossrail 2 construction which could help to reduce their costs over time. It may even reduce the amount of closures needed to build it, although these are likely to be fairly insignificant in the overall picture.
One thing that they could do is look at of there's scope to run more services which don't go into Waterloo, this could allow a more frequent service further out so that you start to build the market for the service increase under Crossrail 2.
As an example, you run a shuttle service along one section to increase the frequency between two points from 2tph to 4tph, with the extra services requiring people to change to carry onwards. Few would do this, however what it would mean is that for those traveling shorter distances these extra services would make their travel a LOT better. There would be advantages for those going into Waterloo in that the passengers going to nearby stations would be spread over more services giving them more of a chance of a seat from when they get on.
In terms of lack of rolling stock, there's the potential for the use of the Crossrail trains for a little while, probably long enough to ballade their books and order more rolling stock.
For instance it should be possible to turn back services at Hinchley Wood (currently 2tph) to increase service frequencies South of there.
