when the 1.5 version comes along you can completely turn off random rebel spawns :)

i dont mind the rebel town garrisons though, you can always starve them. i sort of avoided it early on but once i could train some gaesate (as the aidui) it became a lot more enjoyable. the first time i used them in an assault my 2 units killed around 400 enemy infantry while only losing 5 men.