...what would it be?
I have a few ideas:
Ice like to see one based on the true story of the civil war ironclad CSA Albemarle. The story of tat ship was an important part of the civil war and also an incredible true story from start to finish. In many ways the albemarle was the Bismarck of the civil war.
A movie should be made about the Russian women pilots known as the night witches who waged a heroic and under appreciated air war against the Nazis. Their stories deserve to be remembered.
Lastly, ice like to see a faithful adaptation of "War of the worlds" made as close to the novel as possible.
Seconded on the War of the Worlds, but not so close to the novel as, frankly, it's a bit cold and from what I remember it is more structured like a diary of events. I'd change things up and if made nowadays you could make it an interesting commentary on refugees fleeing the terrors of war which would be an interesting take. Something about the imagery of unstoppable war machines slowly ambling after seething masses of people could make for a pretty powerful movie methinks...
Incidentally I never heard of the Night Witches, but after your mention I found this short animated film which is pretty interesting:
https://vimeo.com/82411203