I am sure many people would enjoy this feature if it were to become available. Including myself.
This of course would require the app to connect to the dvr on which the recording is stored. Not the easiest thing in the world mind you but doable. Hope they take your suggestion seriously.
There are other underlying issues around this, in particular the possibility of DMCA violations. Lets say you record a movie from HBO, then take your tablet/laptop over to your friends house and play it there. That is technically a DMCA violation if that household does not currently pay for HBO themselves. There is a Cloud DVR feature in the works however, but it will not allow you to play recordings from your cable box. It will essentially treat your TWC TV Account as a stand-alone DVR, allowing you to record shows and playback those shows from my TWC TV Account only. So watch for that feature to become more widely available.