I still think one of the best ideas (that shadow has heard prally a thousand times by now) is a mano e mano mode or easier stated as: Solo mode.
In this mode you are the sole benefactor to your covenant. However unlike Loner mode, your opponents in other covenants are also solo as well. So basically, its a one man mode thats fair. This would be very interesting when you are a rogue and you got to go against a warrior, no one's backing you up. The same is true if you are a mage and usually rely on a guard of some sort to attack, not there anymore. If you play things right, you may just become a powerful force through skill. Unlike in loner mode, you may only have yourself, but the enemy doesnt have a whole covenant against you. This makes it much more of a fair man's version of loner mode.