There really should be a mechanism for lawful executions. If some rogue lord from an undead faction keeps terrorizing the countryside and murdering innocent villagers, you should be able to capture them, and then put forth a proposal to lawfully execute them for their crimes and then the kingdom can vote on it like its a policy. If the motion passes, you can then execute them without any negative relations except for the convict's clan, and you should gain honor for upholding the law.
This would open things up a bit, and for the AI as well.
The Empire civil war should have " lawful " executions of " traitors ", no ?
What if Rhagaea is captured, say, by Garios, and executed ? And then Ira ? Would that not then collapse the Southern Empire cause, and her nobles would rush to the Northern or Western camps ? And the Aserai might take advantage of the chaos ......
What if Garios is captured by Lucon ? " Crucifixion ? "
" Lawful " ( in the eye of the beheader ) execution would be a great narrative disrupter, and make things interesting.
But on a different tack, it is anyway better to be feared than loved, and executions should probably not create " negative " relations in the current sense, when haughty nobles scowl at one hatefully and won't cooperate etc. A few executions here and there, " to encourage the others ", should instead build a classic " Dread General " reputation a la Genghis Khan, and Timur, et al, and prove surprisingly good at opening doors and persuading lords and getting your own way, influence, surrenders, etc