It’s quite funny that I blundered into this concept so clumsily. Everyone here has basically come up with the exact same solutions I did except I made my own posts (oops). I’ll add my current diagram of this whole discussion here too.
https://dev.revolutionarygamesstudio.com/api/v1/download/41895
I agree that RuBisCo is not the correct name and that G6P is a much better protein to base the prokaryotic protein-complex (or organelle as you call it) for gluconeogenesis on. I do think RuBisCo would be a cool later addition to the game if different chloroplasts like bacteriochlorophyll for infrared light are implemented and maybe some non-LAWK x-ray/gamma radiation chloroplasts as well. This would mean that CO2 could be fixed with the same organelle and only the energy-capturing organelle needs to change. In terms of playing with different energy sourcing play-styles, creating ATP to create glucose (pyruvate irl) to later create ATP as needed is the ONLY scientifically accurate way, and will still be interesting.
Iron & H2S can still be stored to create ATP, which can then be stored as glucose using RuBisCo and CO2.The iron oxidation can offer other benefits like iron-sheaths for extra protection from predation.
Another very interesting result of separating RuBisCo from the energy-harvesting organelles is the potential in introducing more nitrifying organelles, which reflect nitrifying bacteria irl which are also chemolithotrophs/chemoautotrophs.
heterotrophy vs autotrophy.pdf (109.7 KB)
edit: upon further thought, I think RuBisCo and the calvin cycle make more sense to implement first. Gluconeogenesis essentially takes place already in the game when you digest other bacteria. It would be necessary only when a bacteria is a photoheterotroph/chemoheterotroph, producing excess ATP in the absence of CO2. After all, to generate glucose you need a carbon source. You cannot produce glucose from just ATP. You need ATP + carbohydrate → glucose