Using the Scrum process template, I'd like to be able to create a query that I can use to display a pie chart on my overview page. This pie chart would essentially display a breakdown of PBIs in red/green/yellow status.
Criteria for each might be:
Ideally, this information would roll up to the feature and epic levels (any feature that has a red or yellow PBI is red, respectively, and any epic that has a red or yellow feature is a red or yellow feature, respectively). But that's entirely optional at this point.
For the life of me, I can't figure out how to create a query to accomplish the base query. It might not be possible, and I can live with that.
Is the only solution to this problem to create an extension?
You just answered your own question ;-)
Yes, the only way to achieve this sort of accumulation is to write your own extension.