It's a very fine balance between game mechanics and time to develop it. If you make a system that use voice, there can only be so much variation.
Check out Skyrim and the witcher games. They are both very immersive RP games, but you quickly spot the same answers and voices all over the place. Now if you take robots, they are much easier to make with the TTV software. However the world is not only made of robots so back to square one again.
A good way would be a text based system, where you pick your answer, and the NPC respond by text too. Or a combination of the two options.
Combining text and voice will make the world more alive and you will not have the same high frequent of same voices as most responses will be during a text screne.
It's not easy to make, and I can only imagine true voice interaction when you have a mission that is more or less on rails.
Its certainly an interesting challenge fdev havent done brilliantly with text interactions so far (thinking "tasty cargo") type scenarios. I would be dissapointed in space legs just stayed as boarding ships pew pew and silently leave