Exporting and importing game profiles (files and dengine.net)
Custom game profiles should be exportable/importable. The exported profile could simply be a .dei file with just one profile.
An interesting prospect is allowing submitting custom profiles to dengine.net to a public repository that is browsable via Doomsday's game library UI. This would make it very easy to share profiles with other users. Profiles submitted to the public repo would have to be manually reviewed before being published, though, to check that the PWAD links are valid and the profile works correctly.