How would Val Kilmer's Bruce Wayne have fared in the DCEU?

It's too bad that given Val's health problems in recent years, he can't really be a proper leading man anymore. I think that most people are aware of the news of Michael Keaton allegedly rumored to return to playing his version of Batman in the proposed Flash movie with Ezra Miller. Basically, Keaton would be mentor type of character to Barry Allen and DC's equivalent of sorts, to Samuel L. Jackson's Nick Fury in the MCU. They would somehow cross paths via a multiverse sort of deal like in the Flashpoint storyline.

Again, I could've more easily bought Val Kilmer's Bruce Wayne serve as a mentor type of figure to a young superhero, given that he pretty much played that with Chris O'Donnell's Dick Grayson in Batman Forever.