I'd like to revisit this topic to see if there are some ways to limit snowballing. Obviously, if you gain the advantage, it's rightfully yours, but the opponent should have more opportunities to win it back. And I think there would be more fun/creative play by increasing these opportunities.
Here are some mechanisms that contribute to snowballing:
Citizen soldiers: This means that gaining a military advantage is often accompanied by a proportional economic advantage. Also, by training economy units from military buildings (and military units from the CC), the military infrastructure is largely the economic infrastructure, and vice-versa.
Loot: Resource and experience loot leave the victor with a military and economic advantage. However, promoted units are somewhat slower to gather, which partially counteracts the other advantages.
There are other features that could arguably contribute to snowballing as well, like preventing construction with ranged units, but these contribute much less.
Ideas to reduce snowballing:
Unit diversification and counters: by implementing more sophisticated relationships between the units, we can decrease snowballing by allowing smaller armies to beat larger ones if they have a better composition.
we will need to vary more factors that are often held constant for whole unit classes in 0ad, like price, train time, and HP.
Shift economic contributions more towards civilians (formerly women): This would benefit 0ad by partially deblurring the line between military investment and economic investment, and by decreasing the economic opportunity cost of sending citizen soldier (CS) units to battle. Alternatively, a new eco unit could be introduced to complement civilian gathering abilities, such as a more metal/stone specialized gatherer.
Unit-specific technology tree: By providing players ways to selectively buff particular units, strategy will emerge in the prioritization of "teching into" certain units based on the civ matchup, map, and resource availability. Developments in this area will compound nicely with unit diversification.
feel free to comment some thoughts and suggestions.