Casimero's path to becoming a champion won't be easy since he has yet to have a championship fight. Currently, all eyes are focused on the upcoming Fulton vs. Inoue fight. By the time Casimero becomes a champion, Inoue might have already unified a belt and could potentially decide to move up in weight class once again.
If Inoue will gonna just beat his opponents easily just like he beats those guys in the lower weight division, then there's no point for him to stay in his weight class anymore rather he should continue to fully max his potential until he reached his limit and be one of the pound for pound legend in the boxing history. He is still young and surely he will gonna face some real contenders in every weight division and maybe Casimero will be one of them so that he won't be having any doubts about his skills that he was able to beat every opponent out there that are once great like him in his era.
You have a valid point. Inoue is indeed making history, so it's likely that he will move up in weight class if he believes he can continue to win in a higher division. I'm not sure if Pacquiao is his idol, but if he is, then he should consider following in Pacquiao's footsteps. After all, they are both Asian fighters, and it would be a source of pride for Asians to dominate the boxing world.