Among the tall (180cm+) players, Miku Akimoto (daughter of Ai Otomo) is the most promising as a future Hinotori, in my opinion. She is still very young and raw though, but you can see the volleyball IQ and good movement on the court. She is 16 years old I think and only in her 1st year, so hoping she still improves in the next years.
I also like Emily Iiyama (185cm, MB who hits Opp almost all the time). I'm curious to know if she'll go to a University or a VLeague team. I think she'll improve more if she chooses to go into a University. Kind of built and moves like U20 Nichika but hits like Shion.
I tried to watch all the teams where the U19 and U21 training camp participants (U19 and U21 Training Camp Roster) to know how they play. To bad there's no Seitoku.