That is a cool post. It was very interesting to read, you did a good job writing it.The soul of SatoHika was even in XY where Serena was.
Its first reflection I saw in SatoGekko was the high-five they made in XYZ 028 and it was accentuated by a close-up.
Another reflection in XYZ 028: either Citron and Eureka prompted that Satoshi and Satoshi Gekkouga were really similar. We know that Satoshi and Hikari were really similar too.
And the final reflection in XYZ 028 was the end of the episode when Satoshi and Gekkouga ran:
Now compare it with the well-known scene from DP 004:
I will post further if I find more reflections.