You know, there are still some really Nazi-Fans out there who for sure won´t like that the Nazis in your movie will loose at the end of the movie. So, my idea is that you make a second ending. Let´s say, the first ending could be the normal one (the good guys win like always), but the second ending could be that at least some Nazis escape and so you could make an "open door" for a second part! They could escape, for examle to Mars! What you think?
My second idea is: We all know, that Hitler made suicide. But wait a minute! Until now nobody could find his body. So, why not put Hitler on the moon. Ok, he would be very old now. - Normally. But I researched a little bit and it´s really true that Hitler was working with black magik. So, why not make that possibility that he found the way of never getting older again. At least, if you make part 2, he could appear again! You remember, the Star Wars movie? Darth Vader returned on the next part! Why Hitler not? I know, you finished already filming the first part, but if Hitler doesn´t appear in the first part, let´s do the second part with him! Would be fascinating!