Is it possible to template JIRA issues with pre-filled field contents?
I don't think you will be able to get far without any plugins. What you can take a look at is the Default Values for 'Create Issue' screen plugin. We were using it in the past, however gave up because defaults could be set only per issue type, and no other conditions. I was in contact with the supplier, though, and they confirmed that defaults per user and other extensions were on their roadmap. Makes sense to check if they are already available.