While I see the difficulties with interpretation, I think the threat of retrospective action, will curb a lot of the worse offenders. But I also think it'll be used infrequently and only when its absolutely clear, free from contact or any threat. Does whether they appeal make a difference, as you can't really punish someone for evading injury.
Would Otamendi's head clutching fall get a ban? It was clearly a contrived attempt to get an opponent sent off, but it's not clear as day how you'd demonstrate so.
What about Phil Jones simulation that got Feghouli sent off? They scissored into each other, but Jones reacted to absolve himself. He got the ball and people were quick to criticise the ref, but it was his reaction that got Feghouli sent off. Even in hindsight I don't think you can look at that tackle and be entirely certain that Jones was not hurt in the tackle sufficiently to react that way or punish the theatrical nature. Jones was on the back foot and went across him, studs up, it was well timed and got the ball. Is that less of a simulation because it was in defence, or more of a relevant simulation because it changed the game and ref produced a red early in game? If you retrospectively rescind Feghouli's red, it hardly balances things, but punishment of Jones would seem harsh.
Dele Alli and Jamie Vardy have been hanging out legs or clipping opponents in a way that no one seems to acknowledge. It's one thing to defend the ball, your space and get caught, it's another when you see someone to bungee off. If you can move your path across the player and slow down and flail legs, you can get yours caught up with the guy running behind you.
I think most of the ones I've mentioned and plenty of others, will still be too ambiguous to punish.