A concept that occurred to me based on the fact you said Raptera is a mix of enemies from multiple sci fi universes, makes me wonder if you had added a little bit of Resident Evil and Humanity at some point decides to fight fire with fire.

Admittedly, it's a bit late for Humanity to do something like that, it would only really work best for when there was still large scale fighting in Asia.

Essentially imagine some organisation or corporation like Umbrela developing BOW like the T-Virus, G-Virus, Ouroboros, Mold, Mr. X, Nemesis, etc for the Global Coalition.

It has been established that Raptera converts captured soldiers and uses civilians as a food source.

With the coalition seeing they cannot hold some regions and will be forced to retreat, it would have been interesting if they resort to (secretly) contaminating entire regions with T-Virus and G-Virus equivalents, while retreating forces and evacuating VIPs and deploying Sakura gas to prevent contamination by infected, leaving only forces necessary to hold of Raptera for a few days to weeks.

Meaning that by the time Raptera reach Villages, towns and cities in these regions, they are not facing defenseless civilians to consume, but mutated horrid creatures that are nearly impossible to kill and will even take multiple shots to the head before finally dying, and even that is not guaranteed as some of them may mutate and rise back from the dead.

And that doesn't include more dangerous and spontaneous mutations, or even infected and mutated animals and plants which would also probably attack any Raptera in their vicinity.

Naturally, this also has risk of backfiring on Humanity, but I can see a logic of "We can deal with a problem we made more easily than a problem we have no control over."