Hello,
As for deleting it from their Sent, while technically you could, as long as the Action has permission, it would simply go to their Deleted. Which you would then have to delete (and I cannot remember if you are able to Accept that "Are you sure this will do it forever" requirement popup.
We can implement an action to delete the 'Deleted Items' folder. This poses no problem.
I would send it as someone else. Do you have any SPNs or any other account you could send it from? As long as the manager can see who it is for then does it matter who it is sent by, AS long as you track who requested it?
The issue arises when a requester sends an overtime request. They can find this request in their "Sent Items" folder and take action (approve or deny it). To address this, I want to prevent the system from creating a duplicate copy in the "Sent Items" folder for the user's app, allowing only the approver to take action.