I think it is a good idea to include ethanol as an option. You can put E15, E85, E100 options.
You can make the engine be able to run on ethanol only, or be FLEX (it can chew a wide ranger of options, auto-adjusting things, making more or less power depending on the fuel used). But a flex engine will be less eficient than one that can only take pure gas or pure ethanol (thats because the compression ratio will always be “wrong”, a little bit too low for ethanol, a little bit too high for gas).
Ethanol delivers better output than gas in the same engine, at the expense of autonomy and maybe a little bit of reliability, if you don’t use the right parts.
You can also add a poor country that is an agriculture powerhouse and have lots of ethanol from sugar cane. Gas-only cars don’t sell well here in Brazil, and they also pay more taxes. So it would be up to each player to decide if they want to compete in that market, and if they do they’ll need engines that can take ethanol.
Will the '70 oil crisis be in game? Thats when ethanol began to gain a foothold here. Oil prices needs to be in game as they change the consumer sensitivity to fuel economy (people usually want to spend a maximum amount of dollars per mile running the car, if the gas is cheap enough they don’t mind having more power instead of fuel economy).