Below is a small preview of how the Story Mode in TNA: Impact works. I should warn you that it will spoil a bit of the original story. If you don't like to know about the story, skip the "creating your character"-part of this article, and head straight to "some side comments".
Creating your character
You start of as Suicide (unless you choose to start with one of your previously created characters), and Suicide is one of the most amazing things to ever happen to wrestling. You are getting a title shot, however LAX wants you to take a dive, and do the job. Suicide however refuses to and wins the title. After the match LAX beats Suicide down.
Suicide wakes up in a back alley in Mexico, and can't remember who he is anymore. Mexico, as we all know, is filled with pro bono plastic surgeons that do such an amazing job they can alter the entire appearance of your superstar (Vince Russo himself could not have come up with this storyline). This is the "create-a-wrestler"-part of Story Mode, you can completely change the looks of Suicide and give him all his moves and his introduction. One minor point here is that you can't preview the moves you choose or the introduction, you'll have to wait for your first match to know exactly what you chose.
You can't remember a thing, but you just feel that you should be wrestling, so you wrestle some smaller matches in Mexico. Later on you'll be noticed by a TNA-guy and he offers you a "Foot-in-the-door"-match. If you win, you come to the TNA tryouts. There you will get guidance from Kevin Nash, and he gives you an ultra-strong tag team partner, Eric Young. It seems like you'll be having many frustrating tag matches with Eric as your partner before Kevin Nash once again pops up and talks about the future of your tag team. IGN notes that the Eric Young part of the story mode is perhaps dragged on for too long, so future gamers be warned of a rather boring start of your career. However, once that part is over, the story is interesting to follow.
Some side comments/complaints
IGN comments that the story is very linear. Seeing how you're not a TNA superstar, every storyline can be fixed with a given number of TNA superstars, not like in SvR, where the story changes protagonists if you play with The Undertaker for example. Also, it seems you cannot make a single choice in your storyline, you can't communicate with superstars or anything. You just sit there, watch the cutscenes and play the matches the game gives you. Also, if you lose a match in story mode, you'll have to replay it until you win it. There's no branching the storylines.
You can choose which fighting style you are at the start of the game, but it seems to be a choice that has very little impact. Every fighting style has the exact same moves. Everyone has both the Mexican headscissors and the Death Valley Driver. Also, the moveset seems rather limited. For example, you can only choose from 27 finishers. Normally, superstars can choose up to 7 grapples, but in game superstars only have 4 grapples. How come? Different combinations often make your superstar do the same move, this is to add realism, so that you will not see superstars do moves in the game they'll never do in real life.
You can't really alter your superstars weight, height, gender,... You have to make a model that closely ressembles Suicide, the original superstar you get in the game.