The problem is that alliances just aren’t very useful right now.
In Rise of Nations merchants could travel between cities to increase resource productions. Perhaps something similar could be introduced to DomiNations.
Considering we already have markets and mills, maybe an alliance trading bonus could be added to each that increases the production of food and gold. You could even add some library research to improve the bonuses, or add the possibility to receive a trade good along with the bonus when collected.
Another option is to add a new building altogether, a mercantile. The benefits would be similar to the market and mill but you could have a merchant that “travels” between alliance members and increases gold and food production. The merchant could be upgradable through the blacksmith.
The amount of bonus could be tied to the level of the market and mill, the level of the merchant, or even the level of the alliance.
Alliance levels could be based off of a combination of many things:
- Attacks won
- Defenses won
- Resources looted
- Troops donated
- Wars won (When implemented)
- (Insert more metrics here!)
Also, these metrics would have to scale with the size and average developmental age of the alliance. Perhaps some bonuses are not available until a certain percentage of the alliance members have reached the Gunpowder Age, for example.
Feel free to give feedback on this!