Using python for writing models: How to run models in restricted python mode?

[vinjvinj]

While I understand 2 is very hard (if not impossible) to do in single
unix process. I'm not sure why 1 would be hard to do. Since I have
complete control to what code I can allow or not allow on my grid. Can
i not just search for certain strings and disallow the model if it
fails certain conditions. It might not be 100% secure but will it not
get me at 90%...