Allura has a solid framework for doing imports, and has implemented this for services like GitHub, Google Code and Trac. It covers aspects from Git/Hg/SVN to tickets and wikis.
It would be great to enhance this to support importing & converting data from Bitbucket and Gitlab. The level of integration & conversion may vary depending on the format and structure of the services.
Beyond that, related improvements could be made in supporting ongoing synchronization of Git/Hg/SVN repositories (not just a one-time import). Or importers for JIRA, or improving importing of Allura's own formats.