The main character would have bright green hair and Franziska's sense of fashion.
The rival would looked like a young Manfred von Karma and had a pointy Beard of Evil.
The mentor would be a big, hulking man.
The assistant looked more like Ema.
The detective would be a hot woman.
In-universe example: At the end of 1-4, Phoenix thinks he would've been a prosecutor because Larry framed him for stealing lunch money and Edgeworth thinks he would've been a defense attorney if his actual father wasn't killed by the man who would become his adoptive father and mentor. There's a fan fic based on this premise.
An early concept for Wendy Oldbag gave her a much younger Brawn Hilda look.