I like this idea
I have found that the EW remote now allows you to do this.
If you are editing a song you can still advance the current live song using the remote.
Several times over the years I have used EW, I have been asked to put text LIVE on the screen. You can't do that in EW. While there are some workarounds, it would be great if you could actually type text which appeared on screen as you typed - or edited text.
Such a feature would add a lot of versatility to EW.
An added feature could be an apply button that updates to the live screen/item whiles the edit window is still open.
While I don't like editing and setting up new songs during a program, there are times you just have to do it. I agree with Roger this would be a great feature if possible to implement.