With my vassals conquering more land north (and shooting the myaphisite faith in both feet because they lost half the holy wars they started), I realized I had almost enough land to create the empire of tartaria. I conquered a couple more and started to educate one of my daughters with a bolghar guy, to have an altaic group character to form said empire.
My vassals absolutely hated it. Not specifically in relation score (I had high enough diplo and long reign bonus to offset the "heir educated with rrrrong culture" and "female heir" penalties) but they never, ever voted for her as my successor (I'm using elective monarchy).
They started to vote for some of my cousin or nephew or whatnot. I realised I couldn't sway them, after spending almost 6000 gold pieces to gift all the realm, getting high relation with all my major dukes(90-100 !), they would not change their vote.
So, I murdered him. They voted for his cousin or nephew or something (still my dynasty). Fine ! I murdered him too. Then they chose a random count from my realm, out of my dynasty, really popular apparently, since every single duke voted for him. Sure, why not ? Murdered him.
A less unanimous vote then designed different dukes as heirs to my different kingdoms. So I....murdered them.
And then they elected a retarded,backwater,60 years old childless great-great-aunt from some far-off branch of my dynasty.
My plan was then to murder my elected successors as they came up, hoping that my ruler (78 years old at that time) would die before the survivors recast their vote, hence getting my bolghar-educated daughter elected with my only vote. I even started wars for the sake of putting him in command of 500 men that i'd send against thousands strong ennemy stacks, hoping they'd kill him (he managed to recover from one wound and two illnesses and would later die a peaceful and natural death).
Oh, fuck it, I thought. You won't choose my decently-educated,genius,good-traited daughter just because she's under 16 and foreign-educated, and instead absurdely choose that old hag ? but that's for the good of the realm, you morons !
But by that point I had spent almost as much money on murdering my vassals as I had first to buy them, and I was starting to have pretty bad relation penalties(dishonorable,murdered my kin, murdered my close kin) with many of them for some of the discovered murders. ( and money spent on assassination is "wasted", contrary to the money gifted to your vassals that end up overall improving your realm). I had to change my strategy. Fast.
So I tried something crazy : I revoked every single elector title in my realm. ALL OF THEM. I found myself with something like -300 relation malus for revoking vassals titles. All the realm hated me, but it worked ! they didn't rebel ! not a single one ! (but they created about 16 factions). I had mobilized all the levies of the realm before I started, in the idea that mobilized troops wouldn't be counted as available troops by my vassals, don't know if it mattered.
finally, my old ruler blessed me with his long-awaited death, the bolghar daughter inherited, I redistributed all the duke title to their former holders, I had to start yet again a few wars to accumulate piety and create the empire title, and she was still young enough that I had time to change her guardian and revert her back to original culture.
Phew. Now all is well in the Miaphysite Armenian Elective Empire of Tartaria. Except we're a bit poor.
Shame, we'd could really have used the money ,to rebuild all the level IV cultural buildings that were destroyed in my nine personnal provinces since I briefly had a ruler of another culture group :/ .