One main challenge was likely his physical mobility. Being 600 lbs, it would have been hard to move around. Another could be changing his eating habits as he was probably used to consuming large amounts of food.
In Mystreet, Aaron would be an interesting choice. His mysterious past and combat skills could add a lot to the crossover. For Skymedia, a character who is an expert in technology or has some sort of unique power related to their world's mechanics. When these characters meet, there could be some really cool moments. For example, Aaron might be in awe of the technology - based powers of the Skymedia character, while the Skymedia character could be intrigued by Aaron's more traditional combat skills.
For the Pirate Isles side, a swashbuckling pirate captain like Captain Blackbeard could be a main character. He could bring his tough and adventurous spirit into the Mystreet world. On the Mystreet side, Aaron could be a main character. His strength and loyalty would be interesting to see when dealing with the pirates.
In Aphmau Mystreet, Aphmau herself is very popular. She's the central character in many fanfics. Her strong personality and the various relationships she has make her a great focus. In MCD Switch, characters like Garroth are quite popular. His noble and brave nature often makes him a key character in fan - created stories.
I'm not sure who this 'Harry Travis' specifically is without more context. There could be many characters named Harry Travis in different fictional works or even in real - life anecdotes. Maybe he's a character created by an independent author for a particular, non - mainstream story.
There are so many horror stories with various characters named Travis. He could be from a slasher horror where he's being hunted by a deranged killer. Or in a supernatural horror, he could be a medium - like figure who has to deal with malevolent spirits. In a psychological horror, Travis might be a character struggling with his own inner demons that are manifested in the form of the horror elements of the story.