Hahahahahaha - and whats so wrong with that? Main quests are not affects and neither are faction or important quests (as far as i know) - because they cant die or youd break the game.
Npcs will not Gaurds spawn once a week. You get your just desserts, you murdering bastard.
I ALWAYS save before going on a murderous rampage on a character. Kinda RP it as a dream. When I see Nazeem, for example, I quicksave, chop his head off, kill everyone else and reload.