As you said the powerful figures will recognize him(hopefully) and they can't leave him be especially the world government because he is a threat bigger then whitebeard. So that will bring worlds attention automatically although they can't associate him with rocks but they can present him as an overloard of the old era. What wouldn't make sense is that even the powerhouse doesn't recognize him and constantly underestimate him.

I do hope you wouldn't go about people not finding out who he is or him getting underestimated like those Chinese novel character while the main character himself doesn't bother/care about it. They would assume him to be related to carnes and half the story go about like that, which would be disappointing. This story has much potential so hope you wouldn't go about the cliche route thanks

It has a good start but it might also go down heel quickly if not planned and executed well. I don't know how you wish to go about it but if he wishes to leave the island then realistically he will have to have at least yonko level power to servive in one piece world because the moment people see him with xebecs ship and sword as well as him having yami yami no mi, not only the world government but also kaido and bigmom will do everything in their power to erase his existence. And don't think they will let everything go just because thinking all of these as coincidence because with xebecs identity alone is something they will do everything to delete. However, everything being said I do hope it will be a good read.