Well I'm not sure how many of you have actually tried it but you can buy "quick" food at bars (base game) and cafe's (Get Together). You have to direct your sims more but if you go order before the crowd shows up you can do your eating pretty quick. There is also retail where you can set up food in cases for your sims to grab. I don't know the in's and outs of that but I have sent ghosts to buy ambrosia from retail places made by other simmers that I downloaded. In that the food goes in your sims inventory but you can go to a table with it and eat. There are also of course the food carts (City Living and JA).. it's meant to be quick.
I'm not trying to be a jerk about it..even if it comes off that way. I am saying there are multiple ways to get a quicker meal in the game without asking them to redo a system already in place. Not that I think this sort of desire will be catered too. I think you will basically end up modding in a quicker system.. which is available.
I am going to add that I do hope they do add in for us some type of fast food establishment that works better than our current cafe's do. I just know I avoid them as you can really only order one thing at a time (food OR drink) or it's highly subject to being swiped.