This epiphany came to me when I realized that the main complication of the “Nod are actually the good guys” narrative comes from the fact that they deliberately spread Tiberium, which is a hostile alien terraforming agent that has already caused mass extinctions and irreversible ecological devastation of large parts of the Earth’s surface. The thing is that Nod’s opposition, GDI, can hardly be called a friend of the Earth itself; it primarily opposes the spread of Tiberium largely because it’s a disruption to the Euro-American capitalist order. Hence, Gaia’s Soldiers.

Gaia’s Soldiers, as I imagine them, are a GDI subfaction that don’t exist as a formal bloc but whose membership is largely derived from self-identification and actions. It’s characterized by the following:

• Belief in humanity’s responsibility to act as Earth’s immune system against the Tiberium and Scrin threat. For some, this is a practical position (“we’re the only ones who can”) - for others, it manifests as a religious belief in a conscious Gaia who specifically created humans as intelligent beings to serve as Her immune system.
• Deep-seated hatred of the Brotherhood of Nod, above and beyond that they hold for the Scrin. In the eyes of Gaia’s Soldiers, the Scrin merely attacked Gaia; Nod betrayed her. It is not unheard of for Gaia’s Soldiers members to issue “no quarter” orders or carry out summary execution of captured Nod prisoners.
• Weak identification with the GDI, primarily seeing it as an organization with whom cooperation in the short term happens to be their best shot of achieving their goal (eradicating Tiberium).
• Persistent low-level tensions with GDI’s corporate and military leadership. Gaia’s Soldiers view GDI leadership as disaster capitalists consolidating their power and enriching themselves off of a global crisis; GDI leadership views Gaia’s Soldiers as a time bomb and inevitable coup threat.
• Belief in the GDI’s globalized military apparatus as a necessary evil, with the long-term goal of dismantling it once it is no longer needed and shifting to economic degrowth in the wealthiest regions to allow the natural environment to recover from the devastation of Tiberium.
• Strong advocacy for the impoverished populations of Yellow Zones as victims of both Tiberium and the indifference of GDI plutocrats; practice of maintaining local sovereignty and development aid in liberated Yellow Zones and a marked aversion toward using heavy ordnance or scorched Earth tactics in their urban centers.

Some potential conflict hooks for a campaign/missions, if I ever worked up the motivation to incorporate them into a game mod:

• Gaia’s Soldiers execute Nod scientists who were doing Tiberium experimentation on human subjects. This puts them in the crosshairs of GDI high command, who were planning to Paperclip those scientists.
• A Gaia’s Soldier officer refuses an order to carry out a large-scale aerial bombardment of a city in a Yellow Zone with whom his forces have become tightly integrated and declares that he has ordered his units to shoot down any GDI aircraft that attempt to carry it out.
• The Tiberium Wars are wrapping up, and GDI is emerging the winner. The internal conflict that was being put on the backburner comes to the fore as post-war plans are drawn up, resulting in a civil war.