I actually many times used mobile ordering at Disney because the lines were long and I could get my food way faster via mobile ordering. If it is faster, I am all about it. I remember one time us using mobile and I got my food and the person who was originally in front of me in line when I got in and decided this was dumb was only halfway thru the line. What I find is the mobile ordering is no faster at Universal than counter.
I thought it was only Christmas that caused our extremely long waits, but we went another Saturday and three broomsticks was busy, but not Christmas level and it still took forever. These style quick serve places will need to move faster or there is going to be an issue.
I don't think they can take the order line away ever, but they can do what they do in HP land which is basically almost have a bouncer that stops you and if you don't have a good enough reason to order at counter won't let you go to the counter. I get annoyed, I don't need someone to tell me what do to. I always get 2 of our drinks at the counter as I want no ice (who puts ice in cider?!?) and so many times they step in front of me. It is rude.
I don't think they do that in Epic. They won't want to keep the tables occupied like that.