I see what you mean!
This can be solved by using any of the integrated file sharing services (GDrive, Dropbox or OneDrive). Upload the file there before adding it to your monday.com board. Make sure the drive folder permission is set to “Everyone with a link can view the file”.
Now when you add the file column to a email composer it will send the link to the third party service and not monday.com, your clients should be able to click the link and access the file.
IF the above workaround is not to your liking I would recommend looking at integromat or Flowize as good monday.com integration and automation platforms to fill the gap of native functionality without having to invest heavily in a Custom API development.
Again, We at Omnitas Consulting are available to assist you with any monday.com related consultation. We have specialized in using monday.com to its full extent in order to limit the need for third party development.