Daoist_Over_God
My vote for the Honeymoon. If you’re gonna touch on Mechs, I say go to Evangelion, that world is in desperate need of saving, and Shinji needs a proper role model than the idiots that think putting insurmountable pressure on a teen is a smart idea. For a proper Honeymoon to an anime world, my vote is the Fate Stay Night. Their Magic System would be a great benefit to Spider-Man, as their system is built on finesse as opposed to over powered. Their limited magic forced them to refine their mastery over magecraft, and pushed them to use very little to accomplish a lot. Peter can learn a lot of refinement for his magic and powers.
I'll only suggest universes with power gaining potential.-Worm: plenty of cool powers to be found there, and Peter could defeat the Entities and steal their knowledge.-Highschool DxD: Sacred Gears and devil powers. Peter could kill Trihexa and ExE gods.-Dragon Ball: Get a saiyan bloodline and the super saiyan transformation, greater zenkai too? Study capsule tech.-Pokémon: copy Pokémon powers.-Go to DC Universe and get their cool metals and study the speed force to recreate it. Kryptonian DNA. Lantern tech.-Doctor Who: he can study timelord regeneration, the tardis, lots of things.
My opinion is that I am against going to any anime universe. but sao or fma universe can be nice. (If the universe they go to is the FMA universe, please save Nina Tucker. You can even adopt her. (It's not nice to tell a writer what to do, but I couldn't help myself.)) There are so many worlds to go to as a movie. Maybe Lord of the Rings, for example. (please no harry potter). By the way, I really liked the idea of writing a crossover event with other fanfics. You should go for it. (I'm using Google Translate because my grammar is terrible, sorry)