This will be done completely within the TfL Oyster/Contactless portal. First TfL are moving the Oyster over the Contactless charging system, so that some oddities where contactless can be cheaper than oyster for some journeys, due to the full week’s journeys and all combinations of tickets being taken account of. Part of that process has been releasing the new mobile app and allowing more flexible topups.
https://www.londonreconnections.com/2016/dont-fear-beeper-bus-hopper-tickets-future-oyster/ suggests the full merging of the back office functions of Oyster and Contactless will happen in 2018. This will allow new things like an unlimited bus hopper fare for an hour.
https://www.youtube.com/watch?v=1w95ULafeSY explains one of the common ways where contactless is cheaper, though that’ll change soon. Diamone Geezer has done a good summary of which kinds of journeys are cheaper: http://diamondgeezer.blogspot.co.uk/2017/01/the-same-fare-as-oyster.html
It would be interesting if they could manage to cater for other more complex railcards too such as the two together and family railcard, by agreeing for your accounts to be linked together, and getting cheaper travel on the journeys where you have travelled together.