You can easily bulk-edit policies using the config file - get it, edit it, restore it, reboot. Of course it should be manually tedious, otherwise the effort is not worth it.
It's the only way to change an interface's name BTW.
Second, in the v5.2 FortiOS you have the option to "append" values to a list, in the CLI. Check the "What's New" for v5.2.3 for instance.
"Kernel panic: Aiee, killing interrupt handler!"