How is the resolution of the RNS-E? Can't imagine that is much more than 320x200 or so. While the idea is interesting you might be better with a DVD/MP3 player. Those come with remote and play all kinds of media. A computer needs time to boot, a safe way to shutdown, and some custom application as human interface. Idealy it would be CAN connected to be controlled via RNS-E and not via IR remote.
There is an interesting project on
www.3pmdev.de, a Linux mini-PC controlled via CAN-bus (old Navi D only at this time). Now, once they support the RNS-E, add an internal DVD drive to play video and make that less than the 1k Euro they currently ask for they could have some success.