Oda has been hinting that he wants to achieve a certain dream as the PK. Now, for this, we need to think like how Oda creates his manga. Oda portrays luffy's dream as a "childlike dream" coming from a boy. We also know Oda likes to take reference from real life as inspiration. Now, this chapter was around 2022, so let's see any data in 2022 too
Police officer is the most popular dream for any Japanese boy. Well, polices don't exist in One Piece, but let's see which character is most similar to a police officer
If Zoro is in real life, he'll be a police officer (young boy's dream job). In one piece world, he is a swordsman.
Then, this means luffy's dream is to become the equivalent of a police officer.....to become a swordsman
No wonder zoro was the first one he recruited