Is the Reaper's Due event in the game where you can buy an additional empty slot? Just that it's been a few monarchs now and I'm starting to doubt it... 
province_event = { #Reclaim Land
id = RIP.11705
title = PROSPERITY_TITLE
desc = RIP.11705.d
picture = "GFX_evt_culture_change"
border = GFX_event_normal_frame_economy
has_flag = crown_focus_province
trigger = {
has_province_modifier = prosperity_modifier_3
NOT = {
num_of_max_settlements = 7
}
}
mean_time_to_happen = {
years = 65
modifier = {
factor = 1.2
owner = {
independent = no
}
}
modifier = {
factor = 0.9
owner = {
stewardship = 12
}
}
modifier = {
factor = 0.9
owner = {
stewardship = 16
}
}
modifier = {
factor = 0.9
owner = {
stewardship = 18
}
}
modifier = {
factor = 0.9
owner = {
learning = 12
}
}
modifier = {
factor = 0.9
owner = {
learning = 16
}
}
modifier = {
factor = 0.9
owner = {
learning = 18
}
}
modifier = {
factor = 0.9
owner = {
is_smart_trigger = yes
}
}
modifier = {
factor = 0.9
owner = {
OR = {
trait = administrator
trait = architect
trait = scholar
trait = gardener
}
}
}
modifier = {
factor = 0.9
owner = {
trait = diligent
}
}
modifier = {
factor = 0.9
owner = {
OR = {
trait = scholarly_theologian
trait = mastermind_theologian
trait = charismatic_negotiator
trait = grey_eminence
trait = fortune_builder
trait = midas_touched
}
}
}
}
option = {
name = RIP.11705.a
ai_chance = {
factor = 95
}
owner = {
scaled_wealth = -2.5
}
add_holding_slot = 1
}
option = {
name = RIP.11705.b
ai_chance = {
factor = 5
}
}
}