bpo-8232 has a patch to add an `arguments` parameter to os.startfile(). This improvement is needlessly tied to that issue. It's useful in general as a safer way to execute applications and scripts compared to using subprocess.Popen() with shell=True. It also enables passing arguments to applications and scripts when using the "runas" operation (prompts with a UAC dialog) and "runasuser" operation (prompts with a credential dialog). The latter operations are supported by default for binary executables and batch scripts in Windows 10, and they can be implemented by the progid of any file type.

Setting the working directory with a cwd parameter is not as generally useful, but it's not entirely useless and simple to add at the same time when adding the `args` parameter.