Have you considered Tu Shanshu/tushanshu. Our Avatar cast is in flux, and mostly (all?) Aang-era folks, but we still should have a few. (The downside is that there was a Korra there before, so you'd be inheriting some history.)

The AC is 15 comments a month, and the game is pretty slow and focusing on intrigue and exploration. Extra comments above AC can be used to buy personal plots or clues to the metaplot.