Integrate Etransmit with Revit, don't make it a separate addin install.
Give us the ability to save sets of "etransmittals". I work on several projects, it would be great if I could save the source and destinations for each project almost like export or print sets, instead of saving one group of settings and then having to repath for each project.
If you add separate models using the add file button that aren't linked to the main project you are etransmiting, it should be possible to detach those models in the same way as links or the main model would be.