Ah bleach. That was actually one of the first anime that I watched. It really got me into anime... many fond memories. So, of course, I will have my biases about it. And, to be honest, I am personally ok with religious-esque things being thrown into anime (consider anime with Greek mythology thrown in). As long as it is not directly attacking God. As such, let me describe to you why I think that Bleach is ok.
Let's see... where to begin. I guess that we can start with the Quincy's power. To be honest, this is the first time that I have considered that Ishida's weapon could be considered a cross. Thinking back, I guess that it does have a cross-like look (although, to be fair, so does a typical sword). But I don't think that it has much connection to Christianity.
And, perhaps, it is a "western religious icon" thrown into the anime to make it more interesting. Like a cross repelling vampires. Anime throws in different religious/mythological things (it is easier to note the greek mythological influences in some anime). So, even if that is the case, I would not consider that to be a "misuse of the cross." Granted, my religious background puts less emphasis on the cross itself compared to the qualities of God. In that way, using Christianese symbols in anime does not cross with my beliefs. I understand that this could be different, depending on which Christian tradition you are from.
That being said, I also think that it is not wise to do something because someone thinks that it is ok. Especially if you feel convicted towards the contrary. If you feel that it is a blasphemy against God and can see no way round that fact, then I would encourage you to listen to that conviction. The last thing that I want to do is to encourage you to do something that you feel is wrong.
I hope that helps and I hope that I didn't get too theological.