I have no problem with AI generated text and story but I just can't stand AI voices. Even a hint it is AI narrated and I check out. I would encourage you to consider getting it voice narrated by real people. I'd rather listen to bad/amateur human narration than AI voices.

As a second point - this is very interesting using voice control as game input are there viable alternatives for realtime voice uasing your own GPU?

The entire game hinges on the premise of being able to narrate and understand dynamic text on demand. Pre-recorded messages don’t work for this.