I actually think this is a great idea. For a number of reasons. For one thing, I think it would be more stable than what we have now if not at least the same. Earth 2 would be problematic due to the passage of time, but the main universe itself would work fine. Or we could just pick up where COIE #10 left off with a merged Earth of both Earth 1 and Earth 2 characters. But everyone gets to keep their pre-Crisis histories. The exception being the JSA.