I dont know if you thought about these things, but these are some things that would be great in the tycoon part of the game - I tried to think hard about one part instead of some little random bits. I think game should have regions with their individual preferences of customers (market segments) and different environment (different regulations, costs for manufacturing and importing, restrictions), which would evolve with time.
For example, people in USA prefer different cars than in Western Europe and India is completely different than those two. This could be implemented either pretty simply with only several market segments/characteristics (cheap cars, sports cars, luxury cars, family cars…), or a more interesting way would be something similar to what Democracy did, that game generates a sample of customers which all have different tastes (some want sportiness/utility, some prefer price/utility/reliability, some tameness/utility/safety, other tameness/fuel economy/emissions…) and they would be a representative sample of the whole market. These tastes would be hidden from the player and evolve in time. Player could guess preferences according to what sells and what not or pay for a market research (which would cost money and time and would be slightly out of date when you can react on that research (rolling out a completely new design takes time 
but could reveal that the best selling cars are not what people really want, but have no other choice
But customer preferences are only part of the problem, economy also has a huge impact. If the fuel price is high, even if people prefer sportiness they would take fuel economy more into consideration, and with low fuel prices fuel economy is not very important for most fo the market. Also, state of the economy - customers in India and USA could in theory have similar preferences, but customers in India on average have much less available money to spend on cars. Other things that influence regions are regulations, which can be anything from banning or putting taxes on cars with some specifications (engine size, fuel consumption, emissions, even body types…) to difficulties or outright impossibility of importing/exporting from/to regions (embargoes, cold war… it could be impossible to export cars into Eastern Europe during cold war for an USA company, but only expensive for Western European ones and vice versa). Also, there could be some regional specifics, like patriotism (much more likely to buy local brand, or at least produced locally), tight cities (larger market for small city cars) etc.
Other things could influence manufacturing in that country, like relative tech level of that region, labour skill and price, availability and price of materials and technologies, some regulations could influence not only price, but also some times (lot of red tape = longer to set up a new assembly line for example) and also if you even can buld a factory in that region (Cold war again, or embargoes). Licencing could be also interesting, especially with tight regional restrictions (cold war, embargoes, regulations…) like Fiat licencing with Eastern bloc.
All these things can be based on real life, but it would be more interesting if there was an option to be randomly generated with real life start or completely randomly generated (of course within reason, like economy in USA not going into Indian average within 5 years or consumer preferences changing drastically in one year, but given reasonable enough time, things could change drastically, like Cold war ending in 1960/never or not even starting (in completely random start) or USA and Western Europe becoming the poorest regions in 1990…). You could even implement lobbying influencing regulations and marketing influencing customer preferences to some degree… but could have a chance to backfire
