I don't really see the big deal there, because they can both be classified as Queens, just in a different sense.
The chess piece was designed after C.C., and that is logical considering her status as an accomplice to both Lelouch and Zero, but Kallen is still Q1 in battle and the chess theme most directly applies in that context, so there is more than one symbolic meaning.
But well, that's just how I see it.