actor is already present almost every videogame, visual, and audio episodic and series types except for PodcastSeries. This request is based on active efforts within Google to support cast information for podcast feeds at the episode and series level. I expect this to be actively used in the near future.

Something to ponder :
It seems to me we could land a lot of these commonly used properties (i.e. actor, director, etc.) on a type we are currently missing between CreativeWork/CreativeWorkSeries and the TV, Movie, Radio, Podcast, and VideoGame instance and series types