Ok so I was reading Chapter 0 and when I got to to the part where all the crew members origins are drawn. Garp is is showing visting Ace so that's Luffy, Kuina's father and the dojo so that's zoro. etc. So I got to the part where Hatchan is visiting Shakky and Rayleigh. I got a random thought that maybe during the fishman arc how Luffy asks Jimbei to join his crew. Maybe instead of Jimbei, Hatchan joins. Maybe after the future Big Mam fight, Jimbei is unable to join but Hatchan plays a vital role in the fight to where he joins instead. For all we now Jimbei might die. It seems extreme but Ace died in Luffy's arm so does it really get any more intense then that. Plus during the battle someone important dying is bound to happen.
I also thought that maybe Hatchan was shown because he used to visit when he was young. He's visiting Rayleigh which shows "Roger's" reaction to Shiki's escape. And Hatchan doesn't join.