Since we are talking about cosmetic rewards for penances:
There are multiple cosmetics, which could be “upgraded” by FS with minimal effort, and put in the game in addition to the existing “regular” version.
The penances that are required to unlock those, could reward no penance points. Just put them in for some extra cosmetic stuff to show off.
I would love to see an upgraded version of the “twins - damnation hardmode” dongli (see below), that would be unlocked for clearing (and surviving?) the damnation hard mode at least once with each of the 4 classes.
It could look roughly like this (excuse my MS paint use):
Same thing with the old 1 million (now 500k) kills frame.
Add some glow to it and add it as reward for the final penance tier (reintroduce the 1million kills tier):
Or maybe add a bit of a golden glow around the frame instead (i won’t hurt your eyes by trying to create that effect with MS paint and 20 seconds of effort).
Edit: here is an other one.
Reintroduce the 1500 missions completed penance.
Just add some shiny to the old 1500 (now 500) frame and you got a new frame for the new top tier “missions played“ penance.