Extend autopkg to allow pre and post processing for each recipe.
Add a new process MunkiSetDefaultCatalog as example.
From a user with a default munki catalog, start autopkg run -b MunkiSetDefaultCatalog ...
The MunkiSetDefaultCatalog will be run before all other process and can edit the recipe.
-b and -a can be used multiple time to add all additionnal process before or after the originals.