Oh, I just had another idea I'd like to suggest: Workers may cheaply be upgraded to the lowest-HP foot unit of the previous era. The effect would be called "Mobilization", or "To Arms!" or the like. The conversion would be irreversible, and the converted workers would get a "Mercenary" promotion, meaning that they deduct money from the treasury and cannot be further upgraded. Ancient era: No upgrade possible. Classical era: Worker may be upgraded to Militia. Medieval era: Worker may be upgraded to Skirmisher. Renaissance era: Worker may be upgraded to Longbowmen. Industrial era: Worker may be upgraded to Arquebusier Global era: Worker may be upgraded to Musketeer, Laborer into Rifleman Info era: Laborer may be upgraded to Infantry. This could be useful in sieges (mostly for the AI though), or to get cannonfodder units in times of worker surplus (mostly for the player).