After some consideration, I have a slightly different proposal:
- Change the Basic Oil Processing recipe to output only Light Oil.
- Add the Light->Petroleum gas cracking recipe to the Oil Processing tech.
- Move gas->solid fuel and heavy->solid fuel back to Flammables.
Advantages over the current system:
- Multi-output recipes are deferred to Advanced Oil Processing, so the player can focus on learning fluid and pipe mechanics
- Players are guided to using light oil to produce solid fuel
Advantages over FFF-304
- Players are not forced to build inefficient petroleum gas->solid production, only to tear it down again once advanced oil processing is researched.
- Introduces cracking before Advanced Oil Processing, so the only new skill that has to be learned is working with multi-product fluid recipes, and the possibility of refineries getting backed up. This is the big sticking point, so having it on its own is IMO a big benefit.
- Removes the "problem" that basic oil processing is better in many cases than the advanced version.
- No longer have the immersion stretch that the product that is most complex to obtain (petroleum gas) being now the first oil product. Historically, the first refined oil product was kerosene for fuel. (minor)
This does still defer robots until blue science for lubricant. In my experience this isn't really a big change, since it is extremely common to commit all oil products to researching Advanced Oil Processing before any other technologies. However I'd also consider the possibility of adding an (inefficient) light oil->lubricant recipe if it's desirable for robots to be accessible before blue science.