Agreed! As there is absolutly no religion in the game, which is a shame (even though I'm an atheist), a feud system would bring so much "life" to this medieval sandbox.Maybe there should be some sort of system that justifies executions. A bounty system of sorts. The more a lord raids your villages/sieges your castles, and kills your companions/family members/lords, the less the relation penalty should be for executing him. It would be cool to see a little icon depicting such information on a lord so that you know who's F-ing you over the most. Can give it colors like this: green (no bounty, unjustified execution), yellow (slightly justified), orange (highly justified), red (extremely justified).
People that just raid your villages etc (petty things)would justify for an execution, but definitely not as much, but it can stack up in time if they do it a lot for years. As for killing your family/lords, it would reduce penalties of killing the lords a lot more, making it more of a justified execution. But the same way, if you execute a lord that hadn't really done anything to you directly or very little then the penalties would be more severe. And we also need their traits to matter [-honorable (good traits) + positive relations] with you would decrease probability for them to do actions that would make their execution justifiable (but there's still a chance), and [dishonorable (bastard traits) and - negative relations] would increase likelihood of them doing such actions. It's not too in-depth or complex, it would just breathe some well-needed life into the world... otherwise I don't understand the point of having traits to begin with, if they don't influence anything apart of some dialogue success chances...
The same way a player should be punished - if he just goes around and executes everyone and raids/pillages, then the lords owning certain fiefs/or faction rulers will find it justifiable to execute the player eventually if they manage to capture him. They could also hire mercenaries to specifically go after high-bounty targets. And finally we would have some main character deaths... The bounty would increase more the more renown you get, as well. But if you killed a bunch of lords you would also gain more renown from that. I mean, this system can be really cool if TW just considers the ideas a bit! If they do this then justifiable executions would be a more preferable idea of characters dying rather that dying so easily on the battlefield. Yes, death on battlefield should also happen, but make them more rare. And executions (by both player and lords) would make for a very interesting and dynamic relation system going on. The more "bastard" a lord is, the more chances he does unjustified executions as well, so you better watch out not to lose to such, or your heir might have to revenge you one day and you won't live to see it. I mean, they can make such a good system, it feels like a shame not to try to implement it.