As far as every down TEs, why would you have to get someone to beat him out?
And when is the last time you ever saw a team bench their living legend or even open his job up to an upstart? It simply is not what teams do.
The right way to handle this is to either reason with the player or to outright cut them to eliminate the debate. Otherwise you are going to spend a while trying to secure that one player that is going to make the legend step down.
The biggest problem anyone should have with the situation is that the staff needs to take charge and do the right thing when situationally it is the right thing to do.
Love you Jason, but we really need a faster guy on the field here split wide when it is 3rd and 15.
Knowing Witten's reputation and his nature, you know good and well he politics to be on the field, every play.
By Sit, IMO, that means he is sitting during the whole game.
If it makes someone better to start another player but Let Jason come in a play as well...So be it. But I don't see that as sitting the whole game.
Putting someone in that is not better than Jason just to sit jason just to satisfy the fan base...That would be silly IMO.
If someone can beat him out and play the whole game...So be it.
If someone can be good enough that he earns more playing time...so be it.
As far as your other question when was the last time they benched a player....
Well It goes to another part of your post.
They Let Larry Allen go. They let Emmitt Smith go and they let Demarcus Ware go. All three legends and they could have kept all three if they wanted to but they did not. They knew it was time for them to go.
Also, this team used to never let young players play. That has changed over the last few years...some due to necessity (DBs) and others because someone just was flat out better (romo over Bledsoe and then they Left Dak in even when Romo came back from injury).
It just may be the case that they have yet to find someone who has proven they are good enough as a whole to beat out witten.
However this might make you happy as you can turn a smile upside down and make it a frown.
Maybe they are just to inept to find another TE right now to beat out Jason. Lord knows we went some years after Jay before we finally found our star TE...We may have the same situation during Jason's twilight years and later. So that should give you an extra aha rip on the team point that should keep you happy for some time.