^^ Yes, I also don't think that he can go as high as featherweight and that's it. And it's hard to duplicate what Manny did in his career, and we might not see that happening in boxing.
Going to 122 lbs might not be a big challenge for Inoue now, as he is about to hit his prime. But if he continue to go up, it's going to be a different story, natural featherweight boxer might give him problems even if he can carry his power to that division. So imagine him and Rey Vargas in the ring, or any other featherweight champion.
it would take time to really go up in higher weight division. pacquiao did it but it was not an overnight preparation. he was thrown a lot of criticisms throughout those years. now, if inoue is serious in carving out his own career, he can also do it. but would take years and not only few months. let's see how he will perform in this division. though it is not that much of a change so should be easy for him.
If only Manny Pacquiao had not skipped two division on his going up in weight classes, manny would have bagged another 2 division making it a 10 division champion, but well what happened happens so he became 8 Division champion which I also think is too hard to break. Even with Inoue's skills and popularity, he will have a hard time bagging more division belts because of the weight/strength/resistance possibility. Heavier weight has heavier punches and is more sturdy body that can challenge Inoue's power and resistance to heavy punches.
So in any case if Inoue is something special as well, then he might or can do it. He is under Bob Arum so he knows how to do it because of Manny. If not, then take it slowly, let his body adjust and grow naturally to 126 lbs and higher and we can only accomplished it as we mature and age.
Different boxers have different results even with the same manager/promoter. The problem would be the age. If Inoue take it slow, he might miss some division that will break Pacqiuao's record before he retires, if he take it too fast then he might end up beaten by the heavier boxers. So I really think it is difficult for Inoue to break the 8 division title of Manny Pacquiao.