Fungleff

If we think about it a recurring pattern with Luffy crew is that they join the crew the same arc they are introduced with the exception being jinbei i as he first had to leave the bigmom pirates. And also it would be the eleventh straw hat as there are already ten straw hats. I think the top canidates are either Loki, colon, or gunko. Loki is a solid option but like if he joined that would mean the straw hats would need to get a new ship, same with colon but other than that they would be a great fit for the crew. Now gunko is normal sized and I think she has great potential as a strawhat, like robin and Franky, she is initially introduced as a villain, but maybe later in elbaf gunko will team up with the strawhats and help fight the holy knights. And she is a brook fan girl so there's that too.

It's not rocks first of all because we have seen him multiple times and he has two eyes I like I know sillouhuetes in op are misleading but like they could have covered on of his eyes, and idk if this is actually from oda or not but I've seen a sketch of joyboy before and he didn't have an eye patch he kinda just looked like Rayleigh. I think the one with the eye patch will be zoro. Like he's already missing an eye or at least it's scarred and maybe he will start wearing sn eye patch once he awakens his Hawkeye.