Gradle should generate two scripts on Windows out of the box: both the batch file and the PowerShell script. (This should be easy as the script has already been written by Masashi.) Then there is no need to be able to set the name of the script (but this can still be added as a feature of course).
If the standard start scripts do not suffice for your situation you could still change them of course:
// Same name for the batch file for backwards compatibility.
startScripts.windowsStartScriptGenerator.template = ...
startScripts.windowsStartPowershellScriptGenerator.template = ...