It wasn't outright stated and I can't agree on it. Ichigo thought that he was an Arrancar, but when he asked Ivan whay he as an Arrancar was attacking him Ivan got furied and he didn't like when Ichi actually called him an Arrancar. Of course we've seen that recruting process, but we've also seen how Quilge managed to absorb Allon's parts and got Arrancar's appearence, thus I can conclude that he might have used this technique. So both of us might be correct.
Both of them were called arrancar. Buckbeard actually disposed of them because arrancar pretty much mean nothing to him and he could easily get more.
I think Ivan was indeed an arrancar but after he joined VR's forces and acquired quincy powers, he stopped seeing himself as such and considered himself to be a quincy.
What is interesting about this is if Ivan was Quincy before he died and became a Hollow and then an Arrancar or did he acquite Quincy powers after joining Vanderreich? If the later is correct, then everyone can become Quincy. Thus we can literary see any of current characters gaining Quincy abilities. The same Ichigo and his friends can get such abilities and become stronger.
Also I don't know why Renji didn't want to become Vaizard if he really wanted to get stronger as it's quite obvious that he isn't strong enough as Shinigami no matter how hard he tries.
Well personally I thought the reason Ichigo's Bankai couldn;t be consumed was because he didn't have one .
What I mean is is that after FGT , there has never really been an instance where it could be confirmed that Ichi's Zapaktu survived . Yes , he has that sword and is using GT like b4 , but where is that spirit guy ?? He died coz of FGT in my books and now Ichi is the sole heir of his sword and not a borrower of power like the rest . Hence , his power cant be sealed coz its not a borrowed power , its his power . [Remember that there seems to be no restriction on using Hakudo or whatever] .
Taking a page from Fate/Stay Night , it might be that the zanpaktu are actually spirits of some previously alive / previously independent spiritual beings which were sealed up by the king [which is in my books actually a seal that keeps the shikigami able to use their zanpaktu , a seal guarded by 0th squad , a seal which is pointless now that the spirits of it are being sucked out and making a good reason for 0 squad to show up.] and are now willingly / unwillingly fighting along side shikigami.
The quicny who have a trauma coz bankai was the thing which eliminated 'em thought : lets destroy the source and now we have the story .