Having this constantly visible in combat is useless information, knowing that everyone has all buffs. Would ideally like it to only show missing buffs in combat, similar to other raid buff tracking weakauras. Additionally, could it have tracking for hunter's mark added as a raid buff boss debuff missing?

As far as I know, it's not possible for a clickable button that can cast a spell.
Those buttons are secure.
In restricted environment, there's no API to get auras info on any units.
And the same, there's no way to show/hide secure buttons depending on aura status in combat.
The "alpha" is an exception, it's not protected.