If you had to choose an espada to replace with any soul reaper (with their complete loyalty despite cannon beliefs) which espada would you replace, and with which soul reaper?
You want me to diminish my superior army of Espada by adding a far weaker Shinigami? Why would I do such a thing? I suppose that if you imagine that my end goal was to win against the invading Shinigami, then, yes, I should replace any one of my Espada with @ichigosuggestions. Probably, if I had to chose, I would trade the shinigami army one @grimmjowsuggestions/ @grimmjow-suggestions in exchange for the Ryoka Boy.
If I have to chose from currently serving captains and lieutenants, however, I would take @hirakosuggestions… just for the sweet, sweet irony of it. He would actually be quite useless. And, only worth a trade with Dondochakka.
If I could chose from any officer who had ever served, I would be hard pressed to chose between @unohanaretsusuggestions and @uraharasuggestions. I think having an unkillable murder machine in the First Kenpachi would have obvious advantages on the field of battle, but, of course, Urahara Kisuke is, like myself, considered a Quincy war potential for his intellect and it would be nice to actually have him doing the right thing for once and joining the side that would take down that Wretched Thing on the Empty Throne™.
However, you presume my army was created to rebuff the Shinigami. It was not. Arrancar/Espada are perfectly poisonous to Quincy. My army was designed to invade the Royal Realm… after the Quincy laid waste to it.