How does one attain EMS? I always thought that it was by taking out the eyes of one clan member/blood relative who also has a MS and implanting them into your skull. But people have been saying that the eyes have to be combined (I highly doubt this)
The eyes must be fused somehow, otherwise you could easily do a swap, meaning that Madara and Izuna could have simply swapped eyes [Madara gets Izuna's and Izuna gets Madara's], allowing them both to get EMS without a sacrifice.
As unrealistic as it sounds, the eyes must be fused.