The Request Form feature is a great tool. However, there is limited option to map to fields on the task that is created by the form. Currently, it is ONLY Title, Description, Start Date or End Date.
The ability to map a form field to a custom field on the task would make this tool so much more useful and productive.
When you create a form, you have to tell it which folder the task goes in, so it should provide an ability to map any form field with a custom field that is defined on the target folder.
Please consider making this change