Civilization game have leaders. In my opinion there's should be terrain improvement instead of leaders to give unit attack bonus - we will call it arsenal.
1) Arsenal could give bonus to only units on the same terrain
2) Arsenal could give bonus to units on square with center on arsenal
In my opinion arsenal is better than leaders, because:
1) We don't fix, when leader should been created
2) Leaders are giving too big change to win
Why my idea is brought? In older forums I dedicated idea about providing calculating of attack/defense strength based on distance from homecity. The idea is similar. Giving attack/defense bonuses based on distance from homecity is good idea, but iin freeciv we have large map and small amount of attack/defense points. so providing arsenal terrain improvement is better idea.
We could reduce arsenal to work only on friendly territory, but that's not my based idea.
Why this? Fortification give defense bonuses, but we could allow to get attack bonus by building arsenal in place of fortification. Fortification cannot been build in the same tile than arsenal.