As I understand you have 3 tasks: First you have to submit jobs on behalf of someone, then you have to monitor the job execution and catch the return code, and finally you have to inform the client about the final job status.
I see several different approaches which cover these tasks more or less:
1. Provide a JCL proc which everybody has to use in his private job as a final step. This procedure might invoke Lionel B. Dyck's XMITIP to send an eMail from z/OS to the requester.
2. Provide a JCL proc which everybody has to use in his private job as a final step. This procedure invokes a command file on your Windows workstation via ISPF workstation agent. This command file could trigger anything you want, such as creating a trigger file, sending an eMail, starting a fancy full-colored dialog box, or whatever you like.
3. Send the JCL via FTP to the mainframe. Retrieve the output via GET subcommand and parse it with SED or some perl program to get the return code programmatically.
Hope this helps