So I continued with my first game. Had to give Billy The Bandits. Otherwise I would not have defeated Carthage and the Dark Realm (and Egypt) before the end of Turn 38. Just Russia left, and I'll see if I can do it without doing the mission to deal with the cold in Russia. Not sure if it possible, but we'll see. I still have to fetch myself Kamehameha (and Babylon + Uruk of course). Could possibly be done a little bit quicker, but I also wanted to work on clearing Marco Polo, while not suffering any KOs in battle. Marco Polo is probably going to provide me with more gold than city income ever will.
Yeah, it is a bit of a grind, but for me the challenge in these games is seeing what can be done (most people here would not be bothered to try a 300+ points Sengoku Rance game either). Obviously this is not everybody's cup of tea, and it can get frustrating at times, especially if the RNG gods do not favour you. There are times that I spent 30 minutes on a single defensive fight, against weakened units from a previous encounter (at 10% health, so every attack is basically a one-shot kill), just to get all the bonuses from the fight, rather than just win. 25 free troops (for say six units of 3000 are worth 12000 Gold alone - that is quite substantial).
The Bandits is one of the most overpowered skills in the game - if you know how to manage your brave and occasionally manipulate the field (by changing the positioning of the enemy units - bad units like Drake do have their uses - that said El Draco can be useful on occasion in a second or third playthrough), there is hardly a fight you can't win. For example, the last fight against Egypt, requires just a bit of damage to Cleopatra, dealing with the gun unit in the center, and then the Bandits, will basically win the fight if you luck out with the crits (and at 75% crit rate per attack, that is not that unlikely). The one Arts unit that survives is even helping you because you can heal more than that unit can damage you.
Obviously on the easier difficulties the most overpowered move is Il Milione, since you can turn Marco Polo in a ridiculously effective gold farmer - and use the gold to increase unit sizes quite substantially. That is why carrying over the character clears is the single most powerful bonus you can pick for a new game +.
In my second playthrough on the Japanese version (Hard difficulty) Marco ended up with a unit of 43k - bought lots of reinforcements to increase the payout of Il Milione, and let her fight in all of the multiple battle events (like the 50-story pagoda and Shambhala, and a few character events as well). On higher difficulties, you'll run into the unit cap, so gold is quite useless then. But if you know what you are doing, even Nightmare should not be that hard to overcome.