Not sure if this is the right place for feature requests, but one of the features I think myself and others would definitely find useful are canned responses. These could be saved under a new tab, Completion Tasks, which would allow for sending a reply to the thread or PM where the thread was reported, create a new thread, or create a new PM.
For approval, I think just having a WYSIWIG field where you provide the canned response is fine, with placeholders for things like the applicant's name, the reviewer's name, and being able to plug in question names and responses in a similar manner to what you can do with a thread title.
For denial, I think it can be the same thing, but add an additional placeholder for a reason/explanation. When the reviewing moderator clicks the Deny button on the form, a reason field in the modal will be present so the moderator can describe why the application is being denied. Additionally, an option to require a reason should be present.
Also, while we're on the topic of Completion Tasks, it may also be good to have an option to change the thread prefix (if applicable). Right now, my mods have to remember to update the thread prefixes on our applications manually. We use thread prefixes to be able to track application status at a glance, and currently reviewing applications is a three step operation: reply, approve/deny, and update the thread prefix. It would be great if all of this was bundled under a single click on the approve or deny button.