I am afraid this will not be possible. The general rule applied by the Travelcard and PAYG is that the fare due always reflects the zones travelled through. This applies for example to customers travelling on the Tube today from say Camden Town to Whitechapel.

We're extending the East London line... The line will form part of the wider London Overground orbital network, which will allow you to travel around London by train without having to enter central London.