OK, so I guess we are going for a photographic memory, not an Eididic one. That would be just like "Sense Memory:sight".
BTW, that idea of using copper hemalurgy to steal someone's eididic memory is a great one. Though I have other plans for hemalurgy in this campaign, so I don't think I'll use it here.
I'll see your nit-pick, and raise you an improvised psudo-scientific explaination!
"You see, in the world of Scadrial, the Lord Ruler has messed with human biology enough that "Nobles" brains don't stop growing and expanding their abilities untill the mid-twenties. So amazing mental stunts like photographic memories, dislexia, perfect pitch, and even healing of extensive damage are possible."
Also, in this adventure, there is a steel inquisitor with a special spike that gives him access to Feruchemical Unobtainium. This gives him the ability to store other peoples memories, and then tap those memories by giving them to a third party or the original donor (never himself, it is an external metal for feruchemy). So I think it would be interesting to see what happens when he steals memories from our little "photographer". Willpower damage, confusion, discovery of the SI's ability, etc.