http://confluence.atlassian.com/display/GH/Working+with+Epics lists a feature where creating subtasks will automatically populate the greenhopper Epic/Theme field with the Epic Issue Number.

This is a great feature, however its critically limited as it only works when you use the 'Scrum' project template.

We have more than one team. We have more than one greenhopper project template, yet given the above restriction, only one team can have this feature...

By the very nature that greenhopper supports multiple project templates, this feature should be enabled (or at least configurable) on each custom project template as well.