So you killed someone and are apart of the Dark Brotherhood, that doesn't stop you from becoming arch-mage, guildmaster of the fighters guild, the gray fox, a vampire, and the savior of the world .
There was no consequences for joining certain factions, like in morrowind, and there was pretty much no consequences for doing anything at all, all the important NPCs would just fall unconscious, rather than die.
Despite that, I probably will do everything I can with one character (hopefully there will limitations like in MW).