When editing hosted families (e.g. wall based, ceiling based, floor based etc.) it is not possible to remove the host.
This is a work around.
Place an instance of the family you want to hack in the drawing area. You can insert multiple ones at the same time;
Save the file and close it;
Open a new Revit file from no template. This ensures it is completely empty and Revit will thus create this hacked copy when we do step #6;
Link the previously saved model into this new file;
Go to the Collaborate Tab>Copy/Monitor>Select Link and pick the linked file. Once in C/M mode, click Coordination Settings and make sure that the family types you want to hack are set to “Copy Type”;
NOTE: Not all categories are listed - only Electrical Equipment, Electrical Fixtures, Lighting Fixtures, Mechanical Equipment, Plumbing Fixtures, Security Devices, Sprinklers. (work around - change category to one of these then change it back).
Click the Copy button and pick the families you want to hack;
Finish and exit from this mode when you’re done.
The copied families that Revit created are hacked versions and no longer built inside of hosted templates. Now simply:
select each family and select edit,
in the family file delete the extrusions,
set them to not be work plane-based
save them