We often get stories about hero travelling to another dimension where time moves faster than in main continuity so that the hero could develop some skills or grow up if its a kid hero and then return to main continuity. Well then, if we really want Diana to be gone after WW2 then we can do the opposite story, no? She could have some epic adventure (maybe chasing some escaping Nazi villains) in some alternate dimension. Maybe spends there few years and eventually returns, but then shocker, it turns out that 60 years passed in main continuity.
I think there are many ways to make this work, but to me biggest concerns are these two:
1. We get something like 6 issues story arc that deals with WW2 and then it is not mentioned ever again. No, if we are doing Diana in WW2 then it should be a proper run (maybe a second ongoing book or a series of... mini-series) that explores that time period and leaves room for additional stories if some later writer wants to return to that time period. Last thing we need is an adaptation of WW movie.
2. It is treated as a rumour. WW returns from her exile or some very long adventure in another planet/dimension/whatever and everyone goes "oh, I heard the stories, but I always thought that they weren't real". If that happens then its all pointless. Superman and Batman (and basically anyone who read a history book about WW2) have to be aware of her while growing up, if not then there is no point in her being the first.