It's 1982. Instead of Marv Wolfman, you're in charge of "fixing" the DC Universe. The DC and WB execs think the idea of multiple Earths and heroes is too confusing and they find some of the characters (like Barry Allen) "dull." Marvel is beating you at sales and the prevailing notion is that it's because the DC storytelling approach is "old-fashioned." Admittedly, it's always easier to quarterback on Monday mornings, but have fun with the idea. How do you handle the aforementioned issues?
I'm old enough to remember the pre-COIE DCU. The problem was never the Multiverse or even storytelling in general. It was the fact that DC hadn't developed a unified vision for the DCU like the one that developed during the Silver Age. A key reason for that SA unified vision was what was ultimately revealed to be a new universe, that of Earth-1.
In my opinion, what was needed in 1985 was another new universe, though not the "either/or" approach taken in creating the post-COIE DCU. Instead, COIE has a narrative opening that could have been tweaked for a different purpose. The Big Bang happens again, but instead of only one universe replacing the Multiverse, the original Multiverse is reborn along with a new, separate universe that is cut off from the rest of the Multiverse. While certain individuals know of this Earth's existence, there is no way to access it. The denizens of this new universe, including its cosmic beings, are oblivious to the notion of other universes and believe that theirs is the only one.
This new universe brings new versions of Flash and Green Lantern just as the Silver Age did. Superman's history is not gutted, though it is tweaked here and there. Most importantly, his history with the Legion is preserved as well as his status as the first superhero. The JSA, meanwhile, has been "forgotten," part of a developing storyline for the team.
All titles get new number ones, though Action and Detective keep their numbering and continue as anthology books. This new DCU has no Robin or JLA at first, starting with the debut of Superman and subsequent appearance of Batman.
The beauty of this idea is that when editorial whims change, the Multiverse is still intact and can be discovered by the New Universe and rediscovered by readers.