I've modded the game so all the units cost a tenth of the actual costs. The couple of game I've played showed that the game won't unbalance itself to be war centric. Instead showed some interesting emerging strategy: having 10x units allow to divert some unit from the main force, targeting improvement to remove iron/bronze from enemies. The fight won't raise huge immortal units, as the experience levels typically achieved in games are around the fourth level. Mounted units become more useful for interdiction, as the civilizations needs to keep those resource from enemy to keep pumping units. Research and city development is not impaired, as the unit expense will globally be the same; also the unit upkeep will play an important role, mitigating the number of units on the battlefield.

In summary, now the war could be a viable strategy, and adds a lot of strategy and tactical thinking at the game. I'm looking for possible side effects that this could have on game. For example, there are a lot more of Great Generals in play, also barbarians becomes somewhat too weak to pose a threat to civilizations.

Anyone has other ideas, or would like to playtest the mod?

This will be the base for creating a mod which adds to the game the strategical complexity found in games like the Total War series, so I'd like all the suggestion to:
1 avoid to make this game too much war centered: wars cover an important role only for a limited span on the earth history, and only for some countries.
2 keep the player on fire about enemy units
3 make the unit positioning more crucial to defend oneself
4 make alliances and treaties more useful to keep enemy to declare wars against large coalitions late in game

This may seem a bit off the main topic, I suppose, but I've found that the opposite change also has the same effects. Making units 10x more expensive makes strategic placements and uses much more important.