An idea comes to mind to mess with Snape. No idea how good/viable it is, but I figure I'll lay it out:
Going off of the earlier idea to enchant Snape's Cauldron with some kind of pre-recorded phrases, what if we instead enchant something and load it up with a bunch of pre-recorded reassurances/words of encouragement, to be played if it detects Snape taking away House Points? I imagine Snape wouldn't like his criticisms of students to be undercut with stuff like "You'll get it next time!" or "Don't give up, I know you can do it!".