One of the distinct characteristics of Back to the Future movies is that in the end of each movie (which would be 'episode' in the game case, I presume), all the things just go wrong in the end and the main characters don't have time to go Back to Somewhere (usually future), and the time is ticking and they have to do all this improvised stuff, and all this sense of urgency...
The problem is, most games in the adventure genre (and TellTale games in particular) aren't known well for their sense of urgency. I mean, let's take the last act of Episode 4 of third season of Sam & Max - I knew I could think as long as I wanted to, no one would be summoned to destroy the universe because I will stop him before he does that, no matter how long I linger to solve the puzzle - half an hour or a full hour.
What I'm saying, is that in Back to the Future it's like "Oh my! He has only four minutes left! Oh my! Two! Oh my!" or "Oh my! If something will not be done soon, they're about to fall into the ravine!" and etc. and etc. But how TellTale will transfer this into an adventure game, without making it frustrating for the player or something?
Personally me, while writing this post a not so perfect idea of difficulty levels came to my mind. Like, on easy it's a normal adventure game, on hard the clock's always ticking like in the Last Express. I don't think that's the best solution possible, but a BttF game HAS to have this sense of "shit, everything's going wrong and we don't have any time left!", IMO.