Using ancient texts to highlight or illuminate modern situations or problems is not new. Retelling tales in new forms is not new. Trying to tell the tale of an ancient age to a modern world, in a way that they can understand, is always going to be a challenge. The ancient world of this or that, or in this case Greece, had different mores, rules, hierarchies, traditions, that are so far and away from us, that it is difficult at best, to imagine living there.
Your case for the modernization of Briseis is strong, but what of the case for her, in her time, given what we know, and what we can somewhat legitimately infer. She has a walk on roll, a short speech, and the rest is silence.
Achilles is a rapist, true enough, but can one truly put today’s standards on a time and place so long ago, and make a judgment based on that? The past is different, it can be used to illuminate the present, as you very strongly illustrate, but it is not the present. Perhaps it is just a point of view of mine, but as one goes into the past, it seems fair only to judge it by it’s standards, and then how those standards have changed, and perhaps why.