Howdy?
I have created a tool for SAP GUI with which you can mass-copy of an R/3 user and set initial password as well as permanent password for them. It can also just simply go through the specified range of users and test their permanent passwords. It is a Windows GUI application implemented in Visual Studio 2013 Express in VB.NET. Prerequisite for running this tool is that Microsoft.NET must be installed, version 4.5 or above is preferred.
The tool is call "COE User Manager for SAP GUI" and it is free of charge for both personal and professional use. However, it might be difficult to use it for personal scenarios without having your own R/3 system at home. 
You can download it from SourceForge where I published the application:
>>> Click to download COE User Manager for SAP GUI<<<
Main page on SourceForge: https://sourceforge.net/projects/coeusermanager
Here is the full description:
COE User Manager for SAP GUI is a Windows application which can attach to SAP GUI and execute predefined actions automaically by instrumenting SAP GUI's scripting API. Predefined actions include copying a master user to range of users, testing passwords as well as setting the initial or permanent password for them. The tool aims to ease this kind of mass operations for system administrators typically as preparation for a volume test for the R/3 system, that are difficult to automate with other tools like eCATT. Prerequisite of this tools is Microsoft .NET Framework 4.5. The downloadable ZIP contains both an installer and the standalone executable. The latter is meant for scenarios where you do not have administrative permission for the Windows system on which you want to use this tool.
And a screnshot:
You may implement similar functionalities e.g. in eCATT, but note that eCATT is unable to record and replay login, which is the key of all features of this application. If you are interested in SAP GUI scripting, you may want to read the official SAP GUI scripting API documentation: SAP GUI Scripting API Documentation
DISCLAIMER: COE User Manager for SAP GUI is provided AS IS without official support. I take no responsibilites of any kind of damages you may cause by using this tool. Nevertheless, feel free to report any issues or feature requests via the SourceForge page mentioned above. I will look into it whenever I am not in a lazy mood.
Best regards,
Viktor