How would Super Robot Wars Style Webnovel which focus on Public Domain would works

I want to write Crossover Webnovel where it is basically Super Robot Wars but with Public Domain characters & elements from Literature, Mythology, Fairy Tale & History

The plot is basically there is the convergence event that has been connecting world of Literature, World of Mythology & World of History & these worlds started to the world while MC's Group who come from Our Real World also get send to the war between these three worlds like Adolf Hitler decide to invade Asgard, Surtr are conquer the Cthulu Mythos America