I tried the increased movement from 80 to 260 and the other factions become extremely aggressive and expanded very rapidly. Even the rebels became aggressive and would launch attacks against me and other factions. A lot of the rebel cities would almost entirely empty out and the troops inside would be used to attack faction cities right from the start of the game.

At year 260 Arverni is moving into Iberia, Makedon has almost crushed Epiros and is moving northwest along the coast, towards Gaul, and east into Asia. Carthage has taken most of Africa and is pushing into Egypt. I didn't think extra movement would cause the AI to be so aggressive when it normally moves very slow even on VH.