Tib Sun is one of the most atmospheric games I've ever played which is bizarre looking back on, because of all genres RTS is probably the most difficult to establish a lasting, impacting atmosphere due to the player's detached perspective/presence- Part of the reason I've always pressured the makers of Reborn to consider a singleplayer portion exploring the desolate world through the eyes of an individual.
That concept becomes much more terrifying and real when you consider the fact that creatures like the Tiberium Fiend were roughly the size of a tank and were, to an individual soldier, an impossibly dangerous nightmare. I spent a year or so writing up a pitch for a singleplayer campaign set in the Tib Sun/Firestorm setting following the story of a Nod soldier who undergoes repeated cybernetic ressurections over the course of the campaign, losing his humanity, focusing on stealth and environmental survival mechanics.
The idea wouldn't pan out well in W3D well I think, so I moved on trying to pitch it to other projects.