I want Pekoms to join Strawhats. I do not think that either Pedro or Carrot are any more of a candidate than Marguerite(that I adored) during Amazon Lily arc.
I wouldn't bet very high in the possibility of one of them becoming a mugiwara, but if we'll have a mink in the crew, then Carrot is my choice so far.
Just got past Amazon Lily on my re-read and I'm still sad that Marg didn't join. That said, I think Carrot would be the best candidate if a mink was going to join - since she is a real fighter class female character. I think a lot of people would appreciate that. The only one I, at the moment, really don't want is Pedro. Though I am in complete doubt that anyone but Jinbe will ever join the main crew again.
Unfortunately i also think that the chances of we having more new mugiwara isn't that high. Probably the new ones will be only allies/followers like Bartolomeo and the other guys from the Colisseum…