So you want to push people to burn solid fuel in their smelters and steam power plants to get rid of the light oil? That's nice as a choice, but shouldn't be required. There should be options about what to do with excess oil products. Right now you can do the solid fuel thing, but rushing cracking is also an option
Thermodynamics isn't the only consideration here. Coal liquefication is economically inefficient compared to just pumping oil. With technological improvements it can be profitable these days, but not by much. And it's nice to reflect that in game. It shouldn't be competitive with oil. In reality it is mainly used when a country doesn't have enough access to oil and can't or doesn't want to import it for geostrategic and economical reasons (Germany in WWII, South Africa or China). This can be compensated for when it has a lot of coal instead. Same in FactorioI'm of the opinion that coal cracking should be energy positive. Forget trying to make "realistic" thermodynamics because it's not fun.