A twelve way split-screen in a movie would be fine for a few seconds to show parallel action. Parallel discussions would be horrible.
The only way to make twelve interviews palatable to readers would be in a kind of "Groundhog's Day" format. The interviewer goes through the whole thing with a kind of "been there, done that, when's it going to end" attitude with the interviewer being in the main focus. You'll have to make it really detailed, though, with the interviews being near perfect repeats with the different characters providing (nearly) identical responses to most parts of the interview. The interest would be in the interviewer rather that the characters.
Even then, I think most readers would get bored after just a couple of repeats. I mean, look at the movie "Groundhog's Day." The scene with the radio is repeated just a few times so that you get the idea, then most days start in the middle somewhere.
I think you should introduce the characters somewhere and somehow else. You should also ask yourself if you need twelve characters introduced for later use.
Show an interview or two then imply that more took place. All of your twelve characters are those who made it through the interview. Introduce them to the reader in different ways as a natural part of the story. You can have your main character comment on the interviews in later actions with your twelve characters, or merely recollect parts of the interviews as needed.
You as the author may want to write out the twelve interviews so that you have them in mind as part of your characters so that you can write them consistently and sprinkle information from the interviews into your story.
Do not dump all of that on your readers. Nobody is going to read twelve chapters of background before the story really starts.
For you downvoters:
I was "treated" to a movie last night that tried this very concept. It "introduced" five of its characters in a way similar the proposal in the question.
All five were picked up, one after another, by one person.
- Drive to where character A is, see character A kick ass.
- Invite character A to help an old friend with a problem.
- Character A agrees and gets in the car.
- Drive to where character B is, see character B kick ass.
- Invite character B to help an old friend with a problem.
- Character B agrees and gets in the car.
- Repeat for characters C, D, and E.
Over half of the movie was just "introduce the characters." It was dumb, it was repetitive, and it was boring.
Once all the characters were collected, they went about "solving" the problem.
- All of them get back in the car, drive to where informant Z is.
- Ask questions
- Kick ass
- Unknown killer shoots two people (informant and one of the good guys. Always two.)
- Remaining good guys get back in car, drive to where informant Y is.
- Repeat for four informants.
That was also tedious and stupid.
Do you want to write a tedious and stupid story?
You're probably wondering why I watched something that I obviously disliked.
The reason is that it was on a German TV show called Die schlechtesten Filme aller Zeiten (in English The Worst Films of all Time.)
The movie sucked (it truly earned its "worst film of all time" status,) but the comments by the hosts of the show were entertaining.
The movie was Kill Squad. It is a really bad movie.
Watch it, and you'll understand why I suggest that you do not use the idea of a repeated scene to introduce your characters - especially since you intend to do twelve of them.
The five in Kill Squad were too much. Twelve such scenes in a row would have your readers chewing off their limbs in attempt to escape the trap.
I'm not a writer. I'm that mythical opposite to a writer - I'm a reader.
I'm telling you things from the standpoint of someone who has read (and bought) hundreds of novels.
As a reader, I'm telling you what I will not buy. I wouldn't even read it if you gave it to me for free. That's how bad the idea is. I might start reading it, but after a couple runs around the same block I'd probably put it down and go do something engaging - like cut my toenails or watch paint dry.
One movie did make this kind of trick work.
That was the original The Blues Brothers movie.
The only reason it worked there was because the introduction scenes were more or less just cameo appearances by well known singers and musicians. The introduction scenes were little more than places in the movie for the musicians to stand while performing a "signature" song.