ah right I assumed as much as by this time there would have been a mod for that, even the FF7 fan de-make on the NES had character portraits.
anyway my other suggestion is just to have the names come up but with no words, just so you know who's talking, overall if there's voice, i wouldn't want text that matches the voice, i generally don't subtitle games and in the case of ff8 with voices it will look like a very strange way to subtitle a game.
on the music volume side of things, I was thinking it would be like kingdom hearts, where when the voice acting happens the music drops in volume, and when there is no voice acting it will return to its original volume, but it seems after seeing your Squall's Speech during the Garden Battle video that the music will always be at a lower than normal volume.
it's quite a tough thing to decide as the games were originally designed with mute characters and loud music that drew a lot of attention to itself, it certainly wasn't designed as background music to voiced characters like the ffx was most of the time.
But to me the two videos I have seen sound great, just hearing voices dramatically changes the game, even if you had to sacrifice the music by having it at a low volume at all times, that would be an acceptable loss.