Well, a couple of things.  With the abilities, we could take different abilities after the required abilities for a Champion of God.  There's enough space in there that we can vary between us.  But, there are a couple problems with a Knight of the Cross.  First is the cost.  According to Panda, a Knight of the Cross is only viable at the highest tier - which I think is call Submerged.  Second is the timing.  According to Dresden canon, there are three, and *only* three, Knights of the Cross.  And no spots were vacant until the end of book 5.  Plus, although two of the three Knights of the Cross are now inactive, Harry Dresden holds both of their swords.  So any Knight of the Cross would have to encounter Harry Dresden.