Cut geometry with reference plane
Some objects in Revit (like structural beams) can be cut with reference planes. That is extreamlly convenient, and would be a desirable feature in any possible situation.
Especially cuttin sweeps and blended sweeps in familly edition would allow for great improvements in fexibility. At this moment the only way to cut sweep inside family editor is to model void objects. In some cases that contribiutes greatly to the family complexity.