So lets say I have some heavy business logic which needs to be tested and live in its own file, is there no way to include it in inline / auth0 extend / graphcool-cli code?

not yet - could you create a new feature request for this here: https://github.com/graphcool/graphcool/issues?

definitely! we'll discuss this soon, thanks for bringing it up 🙂

Also have a look at the command line

wt bundle

from webtask.io, because that uses babel, and bundles your code into a single file. More light-weight than webtask imho...