I do personally agree their should be more downsides to being a murderer, if only because making death a harsher experience can then be justified.
I don't see anything to stop a King preventing any known murderer entering their land, could even rally their citizens to expel them, I think those heatvein things still work? The fact murder is not a social stigma in MD says enough for me as-is
How would people feel about being able to kill or jail a murderer, through fightcause within a short timeframe after the event, things like that?