I really don't think there's much of a disagreement here. Although some might want all of Dick's role in Forever Evil to be eliminated (I wouldn't object to it myself), I don't think that anyone is actually predicting that right now. Rather, I think most people want some sort of explanation of why in the world anyone thinks Dick is dead, given that all of two Justice Leagues saw him alive when they emerged from the Firestorm Matrix. So far, the hints we have been given have made no sense whatsoever. And every possible explanation adds complications. For instance, who did they bury at his funeral (surely Barbara at least demanded to see the body)? How in the world would they hope to pull a lie like that over on people whose super senses would have told them that Dick was not mortally injured? What did Dick think was going on while he was recovering in the Bat Cave, did Bruce actually hold him prisoner down there? And on and on and on. In any case, I think it's the word "retcon" that is causing the problem. Maybe "modify and explain" would be less controversial?
One interesting thing about the solution you propose is that it means Luthor would now have no reason to believe Dick is alive. Why would Bruce reveal the deception to him, after all? That would make matters a little more straightforward in terms of people knowing or not (we could just assume no one knows until Dick reveals himself to them). But that would certainly be a modification of the situation that existed as of the end of Forever Evil, as well as a change in Seeley and King's original plans, as early on they said they went into the series under the belief that Luthor and Selina were in on the Big Secret.
Also, as Claude has pointed out, there are threads in Darkseid War that could touch on this (Owlman and Superwoman's baby, particularly). It's possible that whatever is said in Grayson will have to (or at least ideally should) dovetail with whatever is said in Darkseid War. That makes for a lot of balls to keep in the air, if true. But I suppose that's what Bat Summits and DC Summits are for.