Lol there are so many references to regular marik (umbra & lumis dialogue and now Solemn Odion) that I'm pretty sure the character will be added sooner or later.
...Except unavailable skills aren't actually "assigned" to any characters. Those "Marik" skills were just assumed to be for Marik. Could just as easily have been Yami Marik or some other character. (Or no one, since not all skills in the data ever get used.)
Everyone forgets the mind-controlled duels (Keith, Strings, Joey) on purpose. It doesn't matter how many times it is pointed out. Well, they are "forget" or are a bit slow.
Poor bandit keith, he was all wasted when he was controller. He reminded me of the leader of some bikers called Skull Flames in the 5d's manga. Yusei defeated him too, just like Yugi/Joey defeated keith.