Stussy has little relevance to the overall story. You might as well give up now if you think a crewmate is joining on Egghead.
If you think it's better to grasp at characters who are barely developed or foreshadowed then have at it.
Well... I try not to bring why Pedro will join simply because he hasn't been shown "alive" since Tottoland. Get a lot of pushback.
But since you asked, I'll summarize and emphasize.
- Pedro fits an established role in Ship Guardian that supersets Lookout by definition.
- Pedro looks similar to the bronze statue imagined by Luffy right after Skypeia.
- Pedro looks similar to the new Foxy Pirates flag drawn by Luffy. This was during an arc about getting a new crewmate, in particular a Shipwright. Afro! reference which leads to Brook's foreshadowing.
- Robin imagines cats during Kuma's Paw Fruit explanation. A connection from Kuma to Big Cat Mink Pedro.
- Kuma protects the Sunny during the timeskip. Ship Guard duties! connecting to Kuma. Franky mentions this to Luffy and crew.
- Kuma is now relevant to the main story during the Egghead arc. And we see that the Paw Fruit can be copied in S-Bear.
- Luffy alludes to having another crewmate in Pudding if she were to marry Sanji. This shows Luffy is open to a crewmate after Jinbe.
- Luffy and other guys wanted to see a super cool ninja...got cool Raizo instead. Note: Pedro and other Guardians were able to sneak up on Luffy. Nin Nin!
- Luffy doesn't really interact with ninjas in Wano. Why would Oda deprive Luffy those interactions?
- Luffy asks if Vegapunk is a ninja. Apparently Luffy is STILL thinking about ninjas AFTER Wano. Which makes sense because above point.
- Pedro was extremely helpful in Tottoland. He helps be a distraction for Brook stealing a Ponegliff copy AND hurts Perospero enough to free the Sunny and crew from certain doom.
- Yet we the audience did not see his Sulong which are among the very few not seen like Zepo, Bepo, Faust, and Pekoms manga transformation.
- Luffy remembers what Pedro did for him by his name reference while turning back to Gear 5 in the Kaido fight.
- Luffy invited a Jaguar Centaur to join which connects to Luffy wanting a crewmate after Jinbe like point 7.
- Jaguar D Saul was brought back to life. A jaguar coming back to life.
- Will of P
- Ninja Guardian
- Nin Jaguar Dian (Dyin')
- Luffy's crewmates have all been in a Cover Story. Pedro and Pekoms escape from Tottoland? Nox Pirates reunion!?!?
- Pedro fits the mold of being the eyepatch character. A Ninja Pirate!