Currently In our company we have a project like your "Atlassian Markeptplace" Project. It has a Production branch ("master") and a Development Branch ("develop").
This Workflow is a "simplier" git-flow Workflow and just uses master, develop, hotfixes and feature branches.
If we create a feature branch it will simply merge from develop and will only be merged right into develop.
But, if some things are broken we usually create a hotfix branch from master and wanted the hotfix branch automatically back to develop.

Currently Stash only supports the automatic merge from release/ to other branches.

In a talk from some of your guys you talk about the specific workflow here:
http://www.youtube.com/watch?v=WX0hLfaKsWg&feature=youtu.be&t=55m17s

Also I raised a QA at answers.atlassian.com:
https://answers.atlassian.com/questions/315802/automatic-branch-merging-master-hotfix-to-develop