>I wouldn't say it's a broken idea. It's just an idea that doesn't scale. Working in a dynamic codebase - especially a Lisp one - basically means you have to be familiar with how everything you're using works.

That's FUD. Just make your code modular. Lisp gives you tools: namespaces, and systems.

>You can at least count on functions not having side-effects.

The great majority of functions in Lisp don't mutate data.