Support automatic adding of subtasks for particular issue types - add create sub task workflow post function

We are looking at instigating a more formal 'new feature' workflow and we were thinking about using subtasks for it. The basic idea is that all new features require that a design document is written and approved, that a test plan is created, that the feature is implemented etc. What we would like to do is whenever an issue of type 'new feature' is created have the standard subtasks automatically added to it.

Currently the only post functions I can add to Create Issue are:
1. Assign to reporter
2. Create comment
3. Update Issue Field

We would like to see "Add sub-task" added to this list. This would let us add each of the sub-tasks to be created, and would save us from having to write custom code.

Even better than this would be to allow this to be defined when creating an issue type. Currently you can specify:

1. Name
2. Description
3. Icon URL

It would be extremely cool to see a list of default subtasks for this issue type.