About the swig/boost.python thing, one thing to understand is that command line don't work like a programming language. You don't use it for the same purpose, even if it's tempting to just let a scripting language as the implementation of the console.
They don't?! You need a better command line. :P Fair enough, I probably wouldn't want to give someone a full Python interpreter inside a video game. Still, I suspect locking down a full interpreter is easier than inventing, implementing, and fully testing a one-off language with reduced capabilities. Especially because the capabilities will likely need to grow in time as your users become more advanced. It's nice to one day say "Oh yeah, that's actually Python" rather than say, "Oh yeah, we need to re-invent something functionally equivalent to Python but which is expressed in our in-house language." - Rhys