There are porn VA's on Twitter wbo might do this if the dev asked them.
Yeah... but then I'd have to use twitter... so, nope.
More seriously though, adding VA isn't a small, quick, or easy undertaking. Even if I just focused on the sex scenes, or brief clips throughout the game, we are still talking a huge amount of time and effort, just even finding people that sound like the characters. And, they'd have to be willing to do it for free, not an undertaking most people will jump at.
Again, the main purpose of the Renp'py version is to make the Unity game more accessible (and fix a number of bugs... and add in my own fetishes... and, yeah, okay, put lots other of stuff), but this is not a full time job for me. Heck, it isn't even a job, it's a hobby I do for fun when I have time/feel like working on it. I have to pick and choose the things I both think are best for the game, and that I'm excited to work on, that I want to spend my limited free time doing.
And honestly, sound, music, and VA are all things I don't really care about in most porn games. I turn off sound/music in pretty much all of them. Even games with VA I usually mute. So... spending hundreds of hours working on a feature I personally don't care for sadly isn't going to happen any time oon (even if it something some players really enjoy).
If you really, really, need voice, you can press "v" and get the text-to-speech. I use it while reviewing scenes to find typos, and while not... good, it's passable if you just don't want to read.