We don't have much information in movies. In order to change that, I would ask for your help in clearing certain facts.
I have listed these characters and in which context they appear in. What you could do is just to provide context: what do the characters do in these movies, like a short description. I do understand some of these are cameo appearances (a split-second depiction), being shown in credits scene or are shown battling.
You could say something alike shown here in Wikstrom's biography, how the character used his Pokémon to battle but lost. I included Diantha in here because I don't know if, in the movie, she is just shown battling Wikstrom, or were there more scenes showing her.
You can write the descriptions here, in comments, or place them on my talk page. Help would be really appreciated.
Brendan - battle scene (?) (MS006: Pokémon - Jirachi: Wish Maker, MS009: Pokémon Movie - Pokémon Ranger and the Temple of the Sea, MS011: Pokémon - Giratina and the Sky Warrior)
Johanna - (?) (MS011: Pokémon - Giratina and the Sky Warrior, MS013: Pokémon - Zoroark: Master of Illusions)
Lucas - battle scene (MS011: Pokémon - Giratina and the Sky Warrior)
Flint - (?) (MS011: Pokémon - Giratina and the Sky Warrior)
Ethan - battle scene (MS013: Pokémon - Zoroark: Master of Illusions)
Cynthia, Barry - credits scene (?) (MS013: Pokémon - Zoroark: Master of Illusions)
N - looking up to the sky, feeling relieved that Ash and co. calmed Red Genesect down (MS016: Pokémon the Movie - Genesect and the Legend Awakened)
---- Done ----
Gary Oak - choosing Squirtle as his first Pokémon (MS020: Pokémon The Movie - I Choose You!), (?) (MS022: Pokémon - Mewtwo Strikes Back: Evolution)
Diantha - battle scene (MS017: Pokémon The Movie - Diancie and the Cocoon of Destruction)
Zoey, Paul, Roark, Gardenia, Maylene, Crasher Wake, Fantina, Byron, Candice, Volkner, Lucian, Flint, Aaron, Bertha, Cynthia, Barry - credits scene (?) (MS013: Pokémon - Zoroark: Master of Illusions)
Alain - credits scene (MS017: Pokémon The Movie - Diancie and the Cocoon of Destruction)
