Adding in a hawkeye timing delay would be one of the simpler parts of adding in UDRS, for example, say you had the appeal from the bowler, then you had 3 or 4 seconds after the appeal to click "Review" or hit a review button, etc. Then the hawkeye would show up.
It would take quite a lot of work and thinking to get it right though, it's a good idea though, I'll leave it at that, it would add a lot to the experience of being the captain, so it would require a lot of consideration either way. Last thing we want to do, with any feature, is bring something in that doesn't work at all. I think you can see that with Australia inclusion this year, it's an enjoyable mode, sure we can improve it and tweak it more, but that's the kind of thing you can only do with feedback from thousands of people playing the game anyway, not in the actual development time.
Though I will add to that again, personally, I don't think it should added to a specific format/all of them, until it is in use by them as a rule in the real world.