Another option could, perhaps be:
1. Mutant Year Zero - only mutants until they suddenly meet their first animal mutants, then:
2. Genlab Alpha - to find out their backstory.
3. Mutant Year Zero - mutants and animals for a short while until they suddenly meet their first robots, then:
4. Mechatron - to find out their backstory.
5. Mutant Year Zero - an arc or two until they meet Enclave Humans, then:
6. Elysium - to find out their backstory.
7. All combined for an arc or two, then time jump until
8. Grey Death (time jump because I feel that the backstory for Grey Death supposes that the species have been living together for a time)
Eden could of course be mixed in here somewhat if the player's are so inclined, but if they choose to take the ride with Dr. Retzius (or alone), they need to wait until Ad Astra to continue