Well, let's just say that his bankai is a hollow, then whenever he trains with it, wouldn't it be influencing him? Plus, a zanpakto is part of a shinigami's soul. But this is pure speculation by my part.
I'm merely stating that renji's bankai is very similar to a hollow, and I know what his bankai's name means and that. I'm just saying that the energy blasts it shoots look pretty much like cero's while tobiumes are more like fireballs and benehime is like, lazor beams. His bankai in general looks like some sort of wild hollow, that's all I'm saying. But this is all speculation.
And I swear to Aizen, that Komamura better have some new techniques with his bankai like flash step bankai or even better, have his bankai be able to mirror kido spells. Could you imagine what a shakkaho would look like at that size?
Yes, Furosuto means Frost in Japanese.