Here's my own version of this notion:
Code:
monitor_events PreFactionTurnStart FactionType slave
; Iuerion
if I_EventCounter IuerionBanditSpawn > 10 ; cooldown has ended
generate_random_counter sett_001_bandits 1 40
if I_EventCounter sett_001_bandits < 2 ; 2.5% chance
spawn_army
faction slave, sub_faction f_casse
character random_name, named character, age 30, x 52, y 262, portrait barb2
traits SlaveBoiiModel 1 , CommandExperience 3, GoodDefender 1, GoodLeader 1, HaleAndHearty 2, TurnsAlive 2
unit celtic cavalry british riders exp 4 armour 0 weapon_lvl 0
unit gaelic infantry swordsman exp 1 armour 0 weapon_lvl 0
unit gaelic infantry skirmisher exp 0 armour 0 weapon_lvl 0
unit gaelic infantry skirmisher exp 0 armour 0 weapon_lvl 0
unit celtic infantry british slinger exp 0 armour 0 weapon_lvl 0
end
set_event_counter IuerionBanditSpawn 0 ; resetting cooldown
end_if
if I_EventCounter sett_001_bandits = 20 ; 2.5% chance
spawn_army
faction slave, sub_faction f_casse
character random_name, named character, age 30, x 58, y 264, portrait barb3
traits SlaveBoiiModel 1 , CommandExperience 3, GoodDefender 1, GoodLeader 1, HaleAndHearty 2, TurnsAlive 2
unit celtic cavalry british riders exp 4 armour 0 weapon_lvl 0
unit gaelic infantry swordsman exp 1 armour 0 weapon_lvl 0
unit gaelic infantry skirmisher exp 0 armour 0 weapon_lvl 0
unit gaelic infantry skirmisher exp 0 armour 0 weapon_lvl 0
unit celtic infantry british slinger exp 0 armour 0 weapon_lvl 0
end
set_event_counter IuerionBanditSpawn 0 ; resetting cooldown
end_if
if I_EventCounter sett_001_bandits > 39 ; 2.5% chance
spawn_army
faction slave, sub_faction f_casse
character random_name, named character, age 30, x 54, y 263, portrait barb4
traits SlaveBoiiModel 1 , CommandExperience 3, GoodDefender 1, GoodLeader 1, HaleAndHearty 2, TurnsAlive 2
unit gaelic cavalry nobles exp 4 armour 0 weapon_lvl 0
unit celtic cavalry british riders exp 0 armour 0 weapon_lvl 0
unit gaelic infantry swordsman exp 1 armour 0 weapon_lvl 0
unit gaelic infantry swordsman exp 0 armour 0 weapon_lvl 0
unit gaelic infantry swordsman exp 0 armour 0 weapon_lvl 0
unit gaelic infantry skirmisher exp 1 armour 0 weapon_lvl 0
unit gaelic infantry skirmisher exp 1 armour 0 weapon_lvl 0
unit gaelic infantry skirmisher exp 0 armour 0 weapon_lvl 0
unit gaelic infantry skirmisher exp 0 armour 0 weapon_lvl 0
unit celtic infantry british slinger exp 0 armour 0 weapon_lvl 0
end
set_event_counter IuerionBanditSpawn 0 ; resetting cooldown
end_if
end_if
inc_event_counter IuerionBanditSpawn 1 ; increasing cooldown counter every turn
; next settlement
end_monitor
Three potential spawn-points, 5% chance of one of the smaller stacks, 2.5% chance of a larger one (which is also closer to the settlement). All of them with an FM leading who isn't easily killed.