I have created a separate table, expanding the base [task] table, with the prefix of RFS (Request for Service) and manage a separate workflow that needs to go to a review team before being assigned. This will depend on your process entirely, but my suggestion is that it is separate.
We also have a catalog item that is called "internal staff request" which is for simple tasks that are not in the catalog and are not a formal request, like for example making a report, updating a file, preparing a presentation for a client, etc. This one is only available to the analysts and its usage is meant to be very light so that people can always have an option in order to register "all their work" on ServiceNow, especially if you are using Time Cards and want to tie most of it to task work.
