...You know, some time ago, I was thinking about what would happen if Ash were to go for his eighth gym badge at Opelucid City. As this thought continued to haunt me, I also had ideas about how it could fit into my fanfic work if I ever finished the first story. Eventually, my thoughts wondered enough to where I had the whole scenario played out inside of my head (or at least the main points) as well as a way for Oshawott to develop without complete BS happening.
You forgot about the adendum to the "Rule Of Cool". Anime craziness can be justified through real-life physics and/or in-anime physics/technology if its presence can make everyone of importance look even more awesome.
Not everything has to have the "it's just cartoon physics" explanation. Sometimes, it's fun to have those subtle connections exist.
I used to be puzzled about how the group could carry so much stuff around with them, but then I considered the idea that some backpacks are made with technology similar to what is used to hold Pokemon in Poke Balls. Dawn probably wanted to bring a suitcase instead for the sake of organization, but since she only had one dress, she could pull it out of the backpack with no trouble. It would also explain the tables and cookware that can be carried around without a hint of struggle.