not sure about the flags in football (sorry that's soccer for you yanks!!!), just couldn't see it being adopted.
What I do think should be adopted, if VAR is to continue, is like the NFL to have an onfield decision and that can only be overruled if there is clear evidence it was incorrect so any doubt and it goes with the onfield decision. All goals are reviewed and, then like rugby, if the TV official spots something off the ball they show it to the ref and everyone can see and hear what they say and how they make their decisions.
Without that transparency the assumption should be that it is corrupt as otherwise they would just let us hear.
For what it's worth I think from Saturday the goal would rightly have been overturned and Van Dijk should have been sent off. Grays goal wasn't clear and obvious, despite the lines, so would have gone with infield decision (can't remember what it was)