More correctly, the XML would be something more like
<playable>
<player value="human" />
<player value="cpu" />
</playable>
It's not valid XML to have an equal sign without an attribute name (in this case "value"), and it's rather messy to have single, closed tags of the same name on the same XML level.
I suppose it could be interesting to have two versions of a faction, with the only changes being to the XML, to help the AI. Of course, I'd rather see a stronger AI that doesn't have to cheat, but that's well out of the range of a modder, for now, anyway. Lua AIs, anyone?