I'd go for pre-placed buildings, it's the easiest way of implementing it. My initial idea was more complicated than required, but would possibly enable doing it all via already existing buildings.
So tweaked version of Lazy's proposal would be:
Code:
monitor_event BuildingCompleted SettlementName = London
and SettlementBuildingFinished = Dungeon
generate_random_counter my_random_counter 1 2
if I_EventCounter my_random_counter = 1
set_event_counter London_Dungeon_bonus 1
end_if
if I_EventCounter g5_random_counter = 2
set_event_counter London_Dungeon_bonus 2
end_if
terminate_monitor
end_monitor
London_Dungeon (whatever):
public_health_bonus 1 and event_counter London_Dungeon_bonus 1
recruit_pool "Women-At-Arms" 1 0.085 1 0 requires factions {..........., } and event_counter London_Dungeon_bonus 2
If you want it to circle bonuses every turn, then you need:
monitor_event BuildingCompleted SettlementName = London
and SettlementBuildingFinished = Dungeon
set_event_counter London_Dungeon_calc 1
terminate_monitor
end_monitor
monitor_event PreFactionTurnStart (or FactionTurnEnd) FactionIsLocal
generate_random_counter my_random_counter 1 2
if I_EventCounter London_Dungeon_calc = 1
if I_EventCounter my_random_counter = 1
set_event_counter London_Dungeon_bonus 1
end_if
if I_EventCounter g5_random_counter = 2
set_event_counter London_Dungeon_bonus 2
end_if
end_if
end_monitor
Regards