Doesn't etherdelta already do this? And it's pretty good at it
We have a completely different design from ED that allows for real time trading. Basically the speed and UX of a centralized exchange with the security of etherdelta. On etherdelta you have to wait for your order to mine and there is no guarantee you get it, on IDEX trades happen right away and there is no risk of not getting it once you have matched.
Check out a demo video and see for yourself -
https://www.youtube.com/watch?v=RWWdxxJ1PJo