Could you use music as a form of flirtation? And if so, which characters would like that?
I don’t see why not! It’s pretty established that at least a few of the mercs play instruments—Demo on the piano, Medic on the violin, Engie on the acoustic guitar, Sniper on the sax—so that could be an element in their respective story paths.
Playing recorded stuff off of the radio, records, or tapes could also be useful in establishing relationships. Who wouldn’t melt if you gave them a special mixtape you made just for them? A MONSTER, THAT’S WHO