Hi Miranda,
Issues turned into resolving tasks is how we handle issues to stories. As long as the resolving task is the only item that's assigned to the agile team, then the original issue can remain intact, which you want because I assume you want your requester to know when a story is completed by way of resolving object.
As far as the custom form, it's a real whopper with a whole three fields. But that's the point, native Workfront with minimal configuration gets the job done 99% of the time. Complexity should be earned.