I'm going to be blunt with you Dazz; in terms of the Bleach universe, I'm not sure a storyline idea like this would be plausible because mastering Bankai would take that amount of time, and that's less complex than each of the Zankensoki.
While I hate using this example, the Yonko are beings who refined each of their crafts, spanning over more than 100 years; I can assume it's 1000 if not more. Being a master in all 4 of these areas, is impossible to achieve in merely 100 years because there would have to be many practices you would focus on to truly call yourself a master. I'm not sure what your purport Izari to be, respectfully speaking, but I'm assuming it's advanced-class Captain level.
Now, imagine someone like Kenpachi having mastered all of the Zankensoki while more spirit energy than what he can do with; Zaraki himself wouldn't truly be good for RPs because of how broken he will become broken as a character and I hate to see Izari end up the same way. Personally, I would suggest scaling down Izari a bit and keeping him as a captain. That way, he becomes more reasonable because if you're gonna use him in an RP, it has to be in a way where he can be defeated. Not Deus Ex Machina'd like Aizen and Madara was in their stories.
Essentially speaking, Izari is power for power's sake, from what I read on his page and here. I mean, I'm technically the same, but I try to scale Takeji back while putting him on an advanced-lieutenant level. So yeah, I'm not gonna be the only one to say this; I'm pretty sure others have noticed and not said anything yet.
Your idea is going to flop, in summation. If you don't mind me saying.