I think most of these guys & gals are nothing but fodder. The only "important" thing going on is that Ichigo is fighting the original substitute shinigami. He will have a back story, it will involve him getting screwed over, which will 'cause Ichigo to emphasize.
Then, after almost getting killed, Ichigo will go (Bankai, Hollow Mask, Super Saiyan-Viking, or some such other nonsense) & defeat him.
Either that or they're brothers.
"The Rich are there to take all of the money & pay none of the taxes, the middle class is there to do all the work and pay all the taxes, and the poor are there to scare the crap out of the middle class." -George Carlin