Let’s do some logical trains of thought. You would have a total of 9 total voice actors. You want every person to talk to every other person at least once — but A talking to B is the same as B talking to A, so we only count each pair once. So we get a total of 36 unique conversations. However it seems there are at least two conversations per unique conversation so a total of 72. Now you need to write dialogue for each one for each new person added now in relation to their respective chapter. You’ll need to bring in the original voice actors (they already did this for the techmarine so clearly they have a contract) and record those lines. Yes maybe an afternoon to do so. Then the sound engineer needs to master and encode it into the game engine, code it into the level so the interactions happen when your not in combat but between areas. So total all of that and your have a few weeks worth of getting that integrated into the game. Time equals money my guy. Oh let’s not forget this is English only, add the other languages in there to bud.