Now anyone familiar with the entire series is possibly noticing a pattern developing here with Ichigo. It seems that he is literally being written as the Swiss Army Knife of the series. If there is a power out there then he has it. Unlike everyone else in the series there is obvious issues with this being that Ichigo is now shown on one level or another to be some sort of Mimic or Copycat. What I mean by that is he has the powers but not the true nature. I give you these points.
1.) Zanpakuto = Shinigami: Ichigo started out on this level. Whats telling is how he became a Shinigami. First by 'absorbing' most of Rukia's power, bam instant make shift Shinigami. Second by finding his own power, again bam instant make shift Shinigami. All upgrades in power based on sheer force of will. Losses power and then for the Third time like clock work, via special sword device bam instant make shift Shinigami. Notice all times he just becomes a Shingiami with a Zanpakuto already in hand. Now we find out from Oetsu, thats not how Shinigami get Zanpakuto, thus proving he was never a real Shinigami (stated as such in the manga itself). Now Oetsu knew this, Renji apparently and Isshin possibly Urahara as well. If you look at it you can say that the entire time in his role as a Shinigami he has been doing nothing but copying Isshin's natural Shingiami abilities at least via Zanpakuto. Similar names, Getsuga Tensho and then FGT that may have been used by Isshin before, mind you its only insinuated (due to his knowledge of it) in canon.
2.) Hollow Mask = Visored: So granted this was already set up around the second time of Ichigo becoming a Shingiami but his happened doing something uncommon (Shattered Shaft Training) and thus quite naturally and thus far different then what the Visored themselves went through. Other then puttin on the mask he doesnt seem to be capable of the more prominent hollow abilities the masks allows. Granted Questionable at best.
3.) Hollow Form = Hollow: Now apparently such a transformation is not unusual to the like of the Visored.
4.) New Hollow Form = Arrancar: Now this one is the really nail in the coffin if you think about it. For all purposes this form came out of nowhere and had more in common with a Arrancar then a hollow as the original form did.
5.) Fullbring = Fullbringer: Now we can rationalize up and down about how Ichigo has this power, but lets not forget in the manga itself he questions how he would even have a fullbring, literally no one answers the question they push forward with the innate knowledge that he obviously has one and everyone including chad knows that but Ichigo.
6.) Quincy Power = Quincy: Ichigo displayed the use of Blut which is odd now all of the sudden after being around Uryu for like ever he suddenly activates a quincy power instinctively even though Uryu himself has never demonstrated such a power and the power seems to be exclusive to the Vandenreich. This is explained by his mother being a Quincy. Now There would be no problem with this if we hadnt already found out that Ichigo whose father is a Shinigami doesnt make Ichigo a Shinigami either. So what is he?
Well best guess would be Isshin Shiba (Shinigami) + Masaki Kurosaki (Quincy) = Ichigo Kurosaki (Power Mimicry). You pull the two races together you have a variation of Rouge from the X-Men or Peter Petrelli from Heroes. It would seem far fetched but its the only thing that can explain the huge amount of instances where Ichigo has basically attained ever canon races core abilities. Now if there is another explanation I can concede to that just throwing the concept out there.