At this point luffy has already advanced extremely far in both his fruit and haki development. While he might need a bit more time to fully master them further point is he’s already a master in both
So what if his next step is just improving his base abilities next? His crew potentially helping him with that. Him not being as good or knowledgeable in any of the things to there level but still maybe a little something
With him potentially facing off opponents that can potentially negate his fruit powers like shanks and Blackbeard at least he might need to start from scratch again. Only to grow even stronger overall when it’s said and done
For example just to use the east blue recruits
- Get the basics of swordsmanship from zoro
- Get some martial arts tips from sanji
- Marksman pointers from usopp
- Lowkey lowkey if luffy gets the ability to effect the weather he can get some insight from nami
- Etc
Again he won’t be as good as them in their respective categories but picking up something from each of his crew to grow stronger could be cool and also be the thing that puts him on that next next level post pirate king level