I love what you've done with Mods-for-HESK! You've recreated (and improved-on) a lot of things that I did when I forked an older version of HESK (v2.4.1).

One thing I did that I'd love to see you integrate is more flexible use of custom fields. I re-purposed some custom fields to collect more troubleshooting information from ticket submitters -- like their browser's user agent string and their screen resolution. I populated the fields' values with JavaScript, and tinkered with several different display options.

- An option to make the input type "hidden".
- An option to add the "readonly" attribute for text fields if you want to be totally transparent about what you're collecting.

These values can be overridden at the client level, but in my experience, very few people bothered manipulating the auto-populated data.

BONUS FUNCTIONALITY!:
(I never got this far with my mods, but...) form validation would would be awesome! You could add an HTML5 regex "pattern" attribute to text inputs to validate field values on the client side, and use the same defined regex pattern to validate tickets on the PHP side on ticket submission!