Their should be an option, where there is a story mode, with FMV's after each fight of each players quest.

Like for example, eahc characters needs their own bosses (before the sub boss and boss - or not even in that order) . like Milleena and Jade could come back and gang up to try and assinate Kitana.
Mileena and Jade, and kitana all in the one fight could be an option for MK6, as well as a story for before that, like:

kitana - getting over the death of liu kang and goro and becoming the ruler of edenia, conquering more realms etc, find that shang tsung has brought back her deadliest enemy mileena in order for her to be assasinated. Mileena sides with Jade for some reason, and they try to kill her, using minons of their own.

Sonya, now being the leader of her team in the Psecial FOrces or whatever, have nearly wiped out many thretening clans, and now the red dragon are trying to kill her, her rival and sub sub boss could be the new red dragon or black gragon leader. Red dragon and black dragon could join forces in order to bring down her and her team, and eventually take over the speical forces agency and inoutworld and in eart...

etc. etc .etc ya know. just idea's