I think it is a good option, and would be great if it was possible for the IFE system to allow captions to be turned on and off at individual seats by the passenger. However, I've never seen any such option, and it may not even be possible, as the IFE system may not be programmed to support captioning, or the tapes used in the system may not be encoded with captions. It seems like it might be something that could possibly be incorporated into future software upgrades to the new AVOD IFE system (if that system doesn't already support captioning), but I doubt that it would be something they'd add to the current systems in place on the 733s and 737-NGs, or even the current 767/777 system.