I mean, more historical evidence GRRM is always good, but Aenys and Maegor is not exactly a period we’re lacking information about.
Honestly, I would trade Sons of the Dragon for a decent timeline of the Great Game, or anything that covered the Third Blackfyre Rebellion in better detail, in a heartbeat.
A nice novella about the children of Jaehaerys and Alysanne would be good. There are a lot of questions I have about them and their era that we simply can’t answer right now: did Aemon Prince of Dragonstone consider Rhaenys as his heir, or was he actively trying to have a male heir and failed? When and why did Baelon Targaryen marry his sister Alyssa, and was it their idea or their parents’? What did Aemon do to become “of allowed memory”, and why is Baelon known as “the Brave”; Jaehaerys’ reign was one of peace, but were there small conflicts internally or externally that the brothers were instrumental in solving? This is just scratching the surface for my questions on that era.
It also would answer lingering questions I have about the Targaryen dragons at the height of the family’s dragon, well, having. Who went with Jaehaerys and Alysanne to Winterfell? Who was a dragonrider among the nine surviving children? Which dragons, if any, did they ride that were ridden by others?