I'd pay to see a proper ancient aliens film. Prometheus showed us that the engineers visited (at different times) ancient Babylonia, ancient Egypt, ancient Hawaii, ancient Scotland etc. I'd like to see more about those visits, and whether anything went wrong.
In fact, thinking about it, I don't think we have ever, ever had an ancient aliens movie. I cannot think of a single film, not one, which is set entirely in the ancient world and which has aliens in it. (Apart from the brief cameo in Life of Brian.) Even Stargate was set in the present-day.