I'm just trying to understand your thoughts behind it. You argue that we need a res like oil because we have other advanced res. But oil is not more advanced/modern than coal and it is not used that much as coal. So if there was oil in TSO, what would you actually use it for? Using it in some production chains instead of coal doesn't make sense because it actually is not used in any of those. Oil is a resource that is used for transportation and advanced material industries - so you would have to create new production chains so oil makes sense - so what new production chains do you think the game needs to justify the presence of oil?
Maybe you just don't like coal, idk, but coal always was and still is a major energy resource worldwide. The only thing that changed are the machines that convert coal into power. We now have a more advanced industry that are more efficient and generate more power compared to 200 years ago. So the only logic step would be to not introduce oil as a new resource but add new buildings that transform coal into a different energy source that is then used to power all other production chains.
Oil is all about transportation - I don't see any transportation in TSO atm. So adding oil as an alternative to coal is wrong - historically and scientifically. And since you wanted a more realistic approach, well, this is the reality, like it or not