It would be great to have the option to use a service like Stacker (www.stackerhq.com) to build custom portals that display Stackby data to customers, partners, vendors and other third parties.

Stacker uses other apps and even Google Sheets as the backend database for these portals. Their service gives you the ability to construct a wide variety of interfaces that would give the flexibility to build customized interfaces for different types of external user interaction.