Hello!
I noticed there was a similar suggestion around two years ago regarding giving Shamans something like this (Seen here), but being partially completed, I'm not sure if the team considered this finished, forgotten, or denied. Either way, I figure this is at least worth posing the question again, though from a slightly different angle:
Shaman has thematic and mechanical synergies with Ranger and is loosely related to the Druid class. However, if a character receives an animal companion from one of these classes, but has a majority of levels in Shaman, the companion remains a vanilla animal. I think it would be awesome and much more thematic if the Shaman Ghostly Visage effect also applied to animal companions they gain; This would make the Animal Companions an effective "Spirit Guide" for the Shaman, and remains fitting with their synergy in other classes.
I don't think there necessarily needs to be any mechanical changes to the animal companions regarding Shaman's synergy, I think that might be cool (maybe a 2/3's progression, as Shaman usually uses), but I'd leave that to the discretion of the development and balance teams.
Thanks for reading!