just played a game in Huge Marathon with industry era start. few problems
1. sulfur makes huge difference early in the game, without sulfur, u can't even build Musketman, there's no chance a str 8 maceman militia can stand up against enemy rifleman.
2. Unit cost become so high, it's impossible to station an unit in every city. (build a city with no trade route to get warrior and archer, but they can't stand enemy attack, especially the occasional enemy unit which can use enemy road. (build as many rifleman militia as possible)
3. fuel is impossible to get. since automobile and fuel are required for tank, u need to have a heavy industry to have 1/2000 chance to produce one of them. but you can't build heavy industry, u can build medium industry, then wait 128 turns for it to grow..... not heavy, but dense industry, then another 128 turns into heavy industry. well u also need to be extremely lucky, hoping nothing else such as medicine, fashion, liquor pop out in that tile.
man... I've build 50+ refinery in most city, they can't even produce one drop of fuel for my tank!?
Since you can only build light industry after assembly line, and refinery is not too far away, so make fuel to appear in medium industry, and raise the appearing rate higher in dense and heavy industry.
or make the Refinery produce Fuel, just raise the build cost of refinery, so it's not economical to build refinery in every city
4. highway sucks, automatic workers keep building them considering the fact I don't even have fuel