Scripting Language for an XNA RPG

Yo. I'm working on an RPG engine in C# and XNA. We're planning on targeting Windows and Windows Phone 7, but are running into issues with AI interactions and controlling player actions during cutscenes. FOr the most part, everything is extracted using the MVC design pattern, but obviously would break separation of concerns. So the idea is to have an interface (IScriptEngine) that takes an IScriptObject and updates data in the map model accordingly.
I was thinking about putting the scripts in an XML sort of syntax:
<Script Name="MoveNPC_1">
<Action Command="MoveToTile" Target="NPC_1" Value="10,2"/>
</Script>

And have the engine parse it that way. My biggest fear is performance issues and scalability.

>>2
What would those be? I assume performance would be a big one, and placing everything in a giant switch() statement is ugly and horrible, but would be easy.

I'd use LUA or something similar, but WP7 lacks Reflection.Emit, and most .NET based Scripting languages require that.