I really like the idea, too! Keep us updated with progress 
When there is a playable Alpha I would like to give it a test as well.
Can (or do you want) to tell us, what kind of enemies there are? What kind of AI is walking through these tunnels?
And… yeah… maybe you should really change the story a bit, since the entire tunnel system seems to be manmade and it is a bit confusing if you tell that the player will be there as the first person ever^^