You could potentially wrap this funcationality in a Service Broker to make it resuable. I am currenlty using the Exchange Managed API In a project I am working on with appointments so I know the idea if pretty easy to do.

Once you have the functionality wrapping a service broker, you could put a smartobject even in your workflow to execute the recall after Approver 1 finishes their task. 

There are going to be some challenges when you dig into the detail of what you are asking, as you are going to need to track the information required by the exchange APIs to execute the recalls. I imagine it is going to need to know some sort of message ID, so that will need to be tracked by you some how. You might have to write some functionality into the broker to send messages for you so that you can control the message ID numbers.