Iterations to be represented outside the version hierarchy

Currently iterations can only be represented in the version hierarchy, this can be problematic as it's not possible to look at iterations across the hierarchy, for example consider the following, which is typical of our version hierarchy.

major deliverable
milestone 1
milestone 1_iteration 1
milestone 1_iteration 2
milestone 2
milestone 2_iteration 2
milestone 2_iteration 3
milestone 2_iteration 4
milestone 3
milestone 3_iteration 3
milestone 3_iteration 4

Because iterations need to be represented as separate versions and a team might work on multiple milestones in an iteration we can't see a consolidated view of an iteration.

It would be great if iterations and versions could be conceptually separated to allow a view on iteration and milestone hierarchy. Currently we shoe-horn iterations into versions to make this work, but we loose all the date based functionality and releasing which isn't ideal.