I'd like to explain my reasoning behind the above-listed suggestions.
Minor nation techs for Italy and Serbia
As Redrum pointed out technology is sometimes denied to those two nations completely in an effort to promote game balance. Instead of getting rid of their technology completely, I've nerfed it to take away most of the economic boost technology provides. But, there's still enough left on the table (especially at the reduced cost!) to make it worthwhile for them to do technological research. Now the players controlling Italy and Serbia have a strategic choice to make about tech spending, instead of having the one option of 100% units/0% tech for their spending.
German neutral farming in South America
If this map were played without any house rules at all it would favor the Entente. There are three ways of addressing that:
- Restrictions on neutral farming.
- Facilitate Centrals' Zerg rush.
- Facilitate neutral farming for Centrals.
The outcome of a Zerg rush is typically binary: the capital you're gunning for either falls or it doesn't. If the target capital fails to fall at all, then often the game is over with an Entente win. But if it falls too quickly, to the Zerg rush of an expert player, then that can spell a very quick win for Centrals. It's difficult to balance that in a way that ensures the capital lasts just the right amount of time, especially if you're trying to ensure the map is balanced for expert-vs-expert matches, and also balanced for intermediate-vs-intermediate matches. Also this map has excellent potential for very deep, long games. That potential is lost whenever the outcome is decided in the first few rounds.
Neutral farming for Germany in South America is a non-binary way of helping the Centrals. Facilitating German neutral farming in South America would potentially allow Germany access to a large source of additional income. This would allow the Centrals more staying power in a longer game, and would address the concern Schultz raised about Britain's income becoming higher than Germany's. It's also worth pointing out that there's a strategic choice involved for Germany here. Yes, Germany can neutral farm South America (long-term gain), but to do so it needs to buy units for the Bolivia factory (short-term pain).