The environment I'm building the code for is one where about five or six people will end up using my code, and maybe expanding it... I figured doing these kind of checks and giving some solid feedback about errors would make the modules & methods easier to handle.

I think I know pretty much what I'm doing, so I like the flexibility. I can't vouch for the experience the people that will use the code have, so that's why I'd like to do some checking...

I like your idea of being able to bypass the checks a lot; the development environment would always use the checks, but the production environment wouldn't, speeding up the application. In that context, it may be an idea to build a module to set up wrappers (maybe using the sub wrapping module Aristotle suggested), which do the checking. It could then be enabled by a single use statement with a list of method names as a parameter...

I can't wait to start tinkering! But sleep comes first... :)