Feature / List should allow sorting by feature rank

We don't do "releases" for one of our products in the traditional way.  Instead, I have created releases that are just buckets of similar functionality.  This is very similar to what is shown in the blog post @ http://www.aha.io/roadmapping/guide/agile-development.  I want to generate a full list of items that we are working on, however, based on rank order in each release.  In other words, I want to have a view of all my "priority 1" items followed by "priority 2", etc. regardless of what "release" they live in within the product.

I thought "that's easy, just create a list in Feature / List and sort by rank (and then maybe by score)".  You can sort by score, but you can't sort by rank.  Bummer...