@Perona:
If Octopakao was a former boss character,
For all we know, the quote could be referring to the former enemies that teamed up with Luffy in Impel Down.
a girl around the same age as the younger strawhats after 3 older members joined,
There is no evidence of that (her being around the same age as the younger Straw Hats, I mean).
was able to bring down supernovas like Luffy and Zoro so easily to their knees,
So being able to incapacitate the captain is a requirement to join now?
was a powerful fighter fighting Grand Line Pirates since she was a child,
Yet, despite this experience, she abandons the crew when she herself is in danger.
had powers perfectly suited to be a scout or a lookout an essential position in the NW where crazy shit go down on the ocean all the time (thing Capone) that was foreshadowed in chapter 304,
I've read 304; there wasn't any foreshadowing of a lookout to be found beyond Usopp looking out of binoculars and Robin looking for the next island from the crow's nest, which literally anyone on the crew could do.
was a former ally of an evil boss arc like Nami and Robin,
Nami and Robin weren't willing and had ulterior motives, respectively.
was sent flying away by Kuma like the rest of the strawhats,
So was the Pacifista from Shabondy. PACIFISTA 4 NAKAMATE!
was seen reading the newspaper deciphering Luffy's message on screen like the rest of the strawhats,
She didn't decipher anything; she had it explained to her so that the audience could get an explanation.
had of all of her belongings on the Sunny,
Big deal. Wanting her clothes back is a terrible reason to join the crew, especially when it's the only reason.
was brought back into the main story alongside the only strawhat that can't find his way back to sabaody by himself and thus is in an ideal position to meet the crew again,
Even though Zoro would have left on his own if the humandrills hadn't showed up, had a boat and the Biblicard, and neither him or Perona seemed to care that Zoro was leaving with nothing but the Biblicard to guide him.
had no where else to go,
One word: Moria. He's still alive, which leaves him open as an option.
was in the process of maturing, away from her former life of sloth, like the rest of the strawhats,
AHAHAHA no. All she's done is whine for food (food which would be nigh-impossible to get on a deserted island) and complain.
had an almost blank slate regarding her backstory allowing Oda complete creative freedom (how does a 7 year old end up on Moria's ship ?),
So having absolutely nothing for a backstory is a reason for why someone can join the crew now? Quick! Someone let Tonjit know! Or Conis!
acted like a complete idiot at times and had many of the comedic attributes associated with the strawhats
Along with, at least, half of the supporting cast.