I'm part of the dev team so take this comment with the level of distance you want but you should have a look at Tuleap [1].
You get the customization to yet another level as you are not constraint by the fact that templates are shared across your organization. You can tweak and customize every single tracker (issue type) with it's own fields & values without impacting others and without depending on an admin for that. You can deep dive with https://blog.tuleap.org/tuleap-versus-jira-software/
