The External Reports feature (Reports -> External from the menu, /reports/external) was introduced in Beaker 0.11 as a way to link to reporting functionality hosted by or stored in other systems. This was at a time when Beaker's web UI was not themeable (so there was no way to add site-specific links to the Help menu, as we have now) and Beaker was receiving a lot of RFEs relating to reporting, metrics, and data mining.
Since this feature has not been used in any Beaker instances aside from Red Hat's (as far as we know) and even there it was never really used, we should remove it, instead of continuing to maintain it (bug 1201127) or improve it (porting to Backbone).
Sounds good to me. Less to maintain, more time for the important features.
Beaker 24.0 has been released.