We’ve recently been working with client with a similar issue. We’ve changed the process in a way that now engineers loads the finished work to a Sharepoint folder where integromat detects the change, creates the tasks with Link to files (a task and subitem per file), we get the data out, populate metadata of the task and once it is done, a deliverable is generated from the task and emailed to the customer with a link instead of a file, and then task is moved to Billing board.
In a nutshell, we’ve avoided Files column due to mentioned concerns and giving a client more file permission control over who downloads what.
Hopefully, it will help somebody. Feel free to ping me for details.