I thought that any tampering or mods disable Ironman mode.
If there's ways to tamper or mod and still run in Ironman, I don't know how to do that. I'm new to CK2 modding, so my advice isn't perfect, but it's worked for me. So in lieu of a response from one of the experts, here's my suggestion. (I suggest waiting to see if one of the true experts responds, however.)
My method does require making a mod. (I don't know how to save edit this sort of thing.) I assume you know how to set up a mod folder structure and all that.
You'll need to make a file in common/landed_titles folder and define a titular duchy.
Code:
d_my_custom_duchy = { #this can be named anything, as long as d_ is in front, which tells the game it's a duchy
color = { 255 255 255 } #these colors follow RGB logic, so you can set whichever colors you want
color2 = { 0 0 0 }
}
You will need to localize it, so it has a proper name in the game instead of just appearing as "d_my_custom_duchy". For more on creating custom landed titles, see
https://ck2.paradoxwikis.com/Title_modding
In the decisions folder, you can make a decision that allows you to add Viviers and Venaiissin into your custom duchy.
Code:
decisions = { #There are multiple kinds of decisions. Using the normal decisions = { } block means it will appear in the Intrigue menu.
create_my_custom_duchy = { #you can name this decision pretty much anything
is_high_prio = yes # Will show an alert once decision is enabled
potential = { #who can see it
}
allow = { #requirement to press it
wealth = 500 #you must have 500 gold in order to use this decision
prestige = 200 #you must have 200 prestige in order to use this decision
owns = 222 # you must control Venaissin in order to use this decision
owns = 223 # you must own Vivarais in order to use this decision
}
effect = { #what the decision does, once used
grant_title = d_my_custom_duchy #gives you the duchy
c_venaissin = {
de_jure_liege = d_my_custom_duchy #makes Venaissin a de jure part of your duchy
}
c_viviers = {
de_jure_liege = d_my_custom_duchy #makes Vivarais a de jure part of your duchy
}
wealth = -500 #removes 500 gold from you
prestige = -200 #removes 200 prestige from you
}
revoke_allowed = {
always = no
}
ai_will_do = {
factor = 0 # this prevents the AI from ever using this decision even if they meet the requirements in the allow block
}
}
}
This is quick and dirty, but will work; I've used an almost identical setup in my own personal mod for a custom duchy creation. As written, it will make your duchy
not a de jure part of
any kingdom or empire, though I assume drift/assimilation will still work. You will need to localize the decision, of course.
For more on creating decisions, see
https://ck2.paradoxwikis.com/Decision_modding