There is a smarty-lite library available. It doesn't support {section} which we use quite a bit of, however it's a drop in replacement for the templates themselves without the large amount of overhead.

I'll be looking into that further before we decide what to do as it may be a solution.

EDIT: Actually I was looking at an older version. The newer version does support {section}. However, no updates since early '07. That's not a big issue, since if it works, we can alter it if needed if anything needs fixing. So, it's a possible solution.