If I'm being honest I feel Dragon's isn't necessary, we should just get like one or two chapters worth of content for it then that's it, we can already infer a lot of it.
-He was a Marine
-Left after Ohara as he saw the government as despicable
-Founded the revs
-We see the revs grow and flourish in Kuma's backstory
Really all we need to know is who Luffy's mom is and what happened between them, and maybe some stuff from his childhood and adolescence.
Got the Doofenshmirtz backstory