For all the harshness the creators of the Super Mario Bros movie got (and fairly, that movie is a mess), I still have a lot of respect for the poor guy that was handled a controller and was tasked to turn a game where a chubby plumber dwarf fights through a cartoony world populated by turtles and mushrooms with legs to rescue a princess from a group of evil turtles/dragons, into the script for a feature film with real people. Lets face it, as much as Bob likes to see Mario as the ultimate face of Video Games culture, his adventures are closer to an acid dream than a narrative.
The only way a SMB movie could work is if it follows the anime OVA template, which is: everybody that watches them already knows the characters, names, relationships and motivations of everyone involved, so we don't need to spend more than 2 minutes in setting the backstory (and we don't even need to place it somewhere within the cannon, either). And, then again, Nintendo is so protective of Mario that any kind of arc, flaw or trait other than "too much of a hero" will be considered blasphemy.