Okay...
Ichigo, Hichigo and Zangetsu... Too many souls in that body.

Hichigo using Getsuga Tenshou is no surprise. I guess you all noticed that Zangestu's GT was blue, very different from the very dark purple one Ichigo uses in Bankai form.
So my guess is that Hichigo has always been a part of the GT attack, probably even stronger that Zangestu.

Regarding Hichigo's evolution, I guess that Espada would be the ultimate, a top rank one of course, if not top rank. But honestly, having 3 entities to deal with is a lot story wise, at least it's my opinion.