Does it get on anyone else's nerves that, no matter how stealthily you dispatch a guildmate, your key will still vanish and you get expelled? Not terribly realistic. This mod sets out to change that by ensuring you don't get kicked out unless you're actually caught killing the person. Of course, if you already have a murder bounty on your head or get caught killing someone else right after doing the deed, it's not too hard for your guildmates to piece it together. Finally, in the case of the Thieves' Guild, assault will also get you cast out, so be careful.

Note that this mod works only for the Fighters Guild, Mages Guild, and Thieves Guild. Logically speaking, Sithis would be significantly more perceptive than the city guard. This mod alters very little in the way of scripts, and should only have trouble if used with other mods that either A: Alter the expulsion scripts in some way or B:Decrease the murder/assault bounty.
To install, simply extract the contents to Oblivion's Data folder.