Suggested alternative to the proposed oil processing changes in https://factorio.com/blog/post/fff-304

With this mod, Chemical Science is made much more accessible with a reliable (non-deadlocking) setup immediately, while dealing with multi-output oil is still extremely advantageous (though no longer required).

Uses a startup mod-setting for Petroleum Gas being locked behind Advanced Oil Processing. Default OFF.

Changes:

• Basic Oil Processing produces only Heavy oil--inefficiently, encouraging switching to Advanced ASAP
• Chemical science recipe requires only Heavy oil products
  • Electric engine introduces lubricant production and the assembler fluid input
  • Solid fuel introduces chemical plants item-output, and offers improved efficiency for starting to learn cracking 'early'
  • Red wire for the copper cost of current chemical science packs--while hinting to solve Advanced Oil Processing
• Heavy to Light cracking is unlocked with Basic Oil Processing, but optional to use (as a hint)
• By default: Light to Gas cracking is unlocked with Basic Oil Processing for further pursuit of oil if delaying Advanced Oil Processing research
• Solid fuel moved from Oil Processing to Flammables (previously empty!)

UPDATE: Changes below will be from a mod setting to restrict light cracking to Advanced Oil.
Unsuitable due to a lack of distinction between various t1 and t2 products that would both land in the chemical science unlock tier.

Below is only active with the AOP-Gated Gas setting (Default OFF)

• Petroleum Gas and dependent technologies/recipes are unlocked with Chemical Science
  • Advanced Oil Processing unlocks Petroleum Gas from its refinery recipe and:
    • Solid fuel from Gas recipe
    • Only Light->Gas cracking
  • Plastics and Sulfur Processing depend on Advanced Oil Processing instead of Basic
  • These now require Advanced Electronics instead of Chemical Science:
    • Uranium Processing
    • Electric Energy Distribution 2
    • Advanced Electronics 2
    • Advanced Material Processing 2
  • Low Density Structure requires Plastics