The technology was created to replace voice actors. That's the actual purpose. Its very existence hurts their profession and benefits studios. You can not be a studio, use this technology, and claim to care about ethics, anymore than Amazon can claim to care about the workers as it invests in the machines to replace them.
No one is holding a gun to their head forcing them to us AI. They made a choice. There is no "ethical" way to cripple the livelihood of working class people for the benefit of your business. Just stop using the word.
It doesn't matter if you compensate or get their approval, because the fact is the existence of the technology in the industry effectively compels all voice actors to agree to let it use their voice, or they can't get work. It becomes a false choice.
If there was no financial benefit, if it truly made no difference in how much a studio pays in labor or the amount the artists make, there would be no reason for studios to want to use it.