Perhaps quality is a bad term to use here as I don't feel it's appropriate to circumvent the user review section.  Perhaps Compliance would be a better term.  Here's a quick example of things that a "certified" product would be checked against.

Items of Compliance

• Adhere to standard naming convention, both in file and folder (this would need to be clearly defined)
• Adhere to standard folder hierarchy, starting at Runtime
• No extraneous files within Runtime
• Readme includes all appropriate information pertaining to package
• Package generally works as it should (very light touch review like checking that poses don't wipe out morphs for instance)
• Zip names actually include the product name somewhere