In a new project we are working on, we need to be able to connect COX cable and one DVD player to 30 tv's. Each user needs to be able to select a different tv station if desired but at times, we will need to play a dvd for all of the tv's to watch at the same time.
Currently, we will have 30 cox cable boxes in a closet, then connect those via HDMI to CAT6 extenders and then back to HDMI at each tv. We will then bring in a seperate hdmi cable from a splitter off the DVD player.
The only downside of setting it up as you suggest is that you would have to select what to display for each TV at the TV. Might get to be a pain if you have to do it to often.
Otherwise you would need a pretty expensive matrix input selector with 31 inputs and 30 outputs.