An alternative ending where both monsters lose would have worked better

I liked the movie. It was fun, funny, pretty to look at and with entertaining actors. The set design was just amazing! For that alone it's a great watch. But the ending seems like a cop out of a darker ending it seemed to lead up to. A typical Hollywood ending is something I didn't expect for a movie that seemed to actually go somewhere. They kiss each other as vampires? Is this Twilight or what?

I think another variant could have worked much better. The vampire was clearly evil. He kills innocent human beings just to eat. He never tries to find an alternative food source. So he clearly is not a sympathetic monster. And he only wants to look after himself and his family and doesn't show that much passion for anything besides that.

The witch told him that she wanted to spend the eternity with him. While he cursed her to hell. They could both have gotten what they wanted and the people could get rid of both monsters and therefore win. At the end they should have trapped her in the casket by having the vampire hold her down in the casket while they put chains around it. Then they would have throw it into the sea. Now the witch and vampire will spend an "eternity" together at the bottom of the sea because the 2 monsters deserve each other and both are way to powerful to be killed. Firstly, it leaves the ending more exiting. As now the viewer will think about them and what will happen to them down there. Will they start a relationship or just hate each other until they are found and rescued? This way the city has an actual chance to survive and tell the story of the monsters. Maybe there could even be a scene where the female doctor finds them by using ships long into the future and they ask her to close the casket again. A future where they are famous for what they did.