Backup exclude exceptions

Hello, I am managing servers that hosts multiple client. In our backups, we have excluded the folder "vendor" with "*/vendor" since we can easily rebuild it with composer. The problem is that some Wordpress plugins have "vendor" folders in them without composer.json. The result is that if we need to restore the website from the backup, some plugins are broken and we need to track down the exact version to fix it. What I was trying to do is to add exception to rules, exactly what we can do in .gitignore by adding a "!" before the rule. So something like that : */vendor !*/wp-content/plugins/*/vendor
As far as I know, the system does not allow to achieve that, but I wanted to ask before giving up. Thank you!