You know, as poor as your post was... It got me thinking. If Marik actually does become playable (I honestly doubt he will, but eh), what WOULD he use? We already have Yami Marik using his Fiend stuff, Ishizu has Gravekeepers. I guess they could expand on his Plant stuff, but we already have Lekunga and Lord Poison. I guess slimes work if Strings isn't playable, though Yami Marik has Revival Jam.
You may have hit the nail on the head as to why he has not been released so far. I'm guessing that his cards would just expand on the Gravekeeper theme while also maybe throwing in some other random stuff that was in the TCG's Yami Marik structure deck (A lot of it is on this page already) that didn't come with him to Duel Links.
(continued): As for Marik's ace monster, I have no idea. I've seen some people claim it is Ra, but I don't know about that. Maybe he would take a page from his sister's book and have his ace card be a trap or spell. In that case, maybe Necrovalley? Who knows?
Thinking about it... I think his boss monster (assuming they don't go game-original and give him Hieratics or something) has to be Metal Reflect Slime. None of the remaining cards that could be acceptable make sense. It's not like Granadora or Humanoid Worm Drake's going to be it, and I doubt Ra or a variant of it would be either. (They'd have done that for Yami Marik if anyone.)
The problem is a lack of cards to give out. Aside from Yami Marik's level-up cards (most of which are tame enough one-ofs to still be plausible, but I won't mention them here), there's basically Granadora, Humanoid Slime/Worm Drake, Bait Doll, Meteor of Destruction, Tribute Burial and Vengeful Bog Spirit. Maybe a few things like GK's Ambusher or Cursed Fig could barely pad it out. But eh.
Aww! Thanks so much! These are so You remind of a couple of other Marik fangirls I know. We all like to write fanfiction about him, and we all duel on here too, sometimes. But I'm the only one who can't do fanart to save my life XD :)