Set this up back when I used XBMC. Would love to see it implemented on Plex! You can go pretty deep into PseudoTV with scheduling and creating real/fake channels which I'm not to fussed about for any potential Plex feature.
I've set up a couple of playlists that do the job here to an extent but it's that spontaneous viewing element that I enjoyed about PseudoTV. Cutting into shows and movies halfway never really bothered me either (especially if you're half watching TV half on a laptop) - say you flick through some channels late at night and land on the last half of Die Hard... I'd happily stay on that channel and watch those 45 or so minutes but I wouldn't want to watch the whole thing from the start sometimes.