I gotta be honest, I don't know shit about symphogear after the first season. I do know the names of the characters and the songs, but that's it.
So, the Symphogears are based on mythical weapons. Gungnir the Striking Spear, Ichiival, the Magic Bow (apparently its also called Ichaeval so idk) and Ame no Habakiri, the Fatal Blade. (These are the names of the main songs in the first season).
So, I was wondering how to connect these to the MC, then it hit me. EMOTIONS. Unlocking these weapons through a difficult experience (like how Hibiki activated Gungnir through wanting to protect someone [might be courage]).
After a while (or when the author gets bored), you can activate the so called power of LOVE. In the series, 'FIRST LOVE SONG' is the title of the first "duet" with the 3 main characters. Combining the weapons into one wouldn't make any sense, so I was thinking some kind of spirits possesing the weapons/mc and then all of them being able to move freely.
P.S I know Hibiki uses her fist to fight and idek about Chris, but well, I just hope that whoever uses this idea think it through more than I did.
p.p.s make sure to listen to the symphogear songs, they're great if you like listening to anime songs.