Why not leave it the services as they are, rather than looking for a solution for a problem which doesn't exist...
There isn't that much untapped demand which isn't already served by the 3.5 trains per hour.
Perhaps because people are mindful of how long it can take for projects to come into being (just when is Thameslink 2000 due to open again?).
As such, and bring in mind that passenger growth is over 4% which means something that is fine now may not be in five years time, it is not suppressing that people are inclined to discuss projects that might be 5, 10, 15, even 20 years off.