So uh, I'm pretty new to all of this but I really wanted to give modding a try! As such, I decided to make a voice pack for Cordelia from Fire Emblem: Awakening over Lucina, intended to be used for her Cordelia-based costume (c03). I may decide to make more of these sort of things in the future; I actually had a lot of fun testing everything out!
Many thanks to ZukeG for helping me out with the process of testing. He's also written up instructions for installation in the readme file, including how to install this voice mod so that it only applies to one costume slot. Though intended for the Cordelia-based one, you can go for any one you choose (though I don't see why you would, haha).