I'm looking for a simple mechanism to require certain fields be set before a backlog item can be put into a status or range of statuses.

Ideally, I would imagine this would work similarly to how the Required / Soft Required fields currently work. In the Administrator page for Backlog list types, every possible status would have a mechanism to pick fields in the Backlog Item that would be required before that status could be set. For instance, if I had a status of "In Progress", perhaps the Description and Team would be required before that could be set. If I had a "Done" status, I might require the same fields plus maybe something like an Owner field. And for it to be in an "Accepted" status, I would maybe need to have a Deployment Details flag set as well.

This would go a long way towards making sure backlog items have the information they need as items move through the status workflows.