Hello,
I just wanted to write to say that this appears to be filed as a feature request. I want to make sure this is referenced here for anyone coming across this thread and wanting to vote for this feature inclusion: APIM Salesforce operation to delete objects
For now, you can only use the included functions to retrieve deleted objects, but can't actually delete them yourself. Here is the documentation for this ability, for reference: Execute Salesforce Operation Assertion - CA API Gateway - 9.3 - CA Technologies Documentation
On a side note - I'm considering making this a discussion type rather than a question, as a question will have a "right answer", where-as this topic is more requesting ideas on what can be done in lieu of the missing functionality. So just a heads up, I may be converting this. I also found what appears to be a duplicate of this, so I will likely remove that one while I'm at it.
EDIT: I have converted this to a discussion from a question now.