My thinking is that you may be able to automate a packaged workbook export using tabcmd and some database restrictions. I would check out this thread:
Hi Naquiyah. I hope you're doing well. Do you have any data available that has the user with what client data they can see? If so, then you can just blend this in with your primary data by client id and apply a filter on the secondary source to limit down to just their client id data when rendering on the server. This is what we do all the time, let me know if you want more specifics.