Adding this as a feature request here for the open PRB0215299. Feel free to enter cases referencing the PRB if you agree it should be implemented.
As it stands out of the box you can delete an active revision without any warnings. At that time the engineering for that part is also purged. If the part and rev are active materials on a BOM it will allow you to delete the part as well with no additional warnings.
I submitted an enhancement request to have at the least a warning display asking double sure you want to delete as it does for revisions with product configurator configs. At the most configurable at the company level maybe disallowing deletion of used revisions.
We have had revisions errantly deleted which in turn threw BOM on other parts into a tizzy and required us to engineer from scratch.
Just passing along 
