Hello Janus,
No, it is not possible to extend TestComplete in this way.
To accomplish your task in TestComplete as you want it, you will need to re-create the Load Testing functionality from scratch.
Another approach to your task may be using the Distributed Testing approach - run several copies of your client application on several PCs, and run the same tests for all running instances of your application by using the Network Suite feature. The number of concurrent users will be restricted by the number of PCs you have, but you will not need to develop a complex plug-in for TestComplete.
