I feel that Vinny is going to grow as an antagonist. He is like Tommy, but on crack (not that Tommy usually is not on crack).
Not only he is an asshole like Tommy, but he is a freaking dangerous one that will not only shit in your bad and fuck your mother, but also kill you.
I mean, for the plot to go foward we need an outlet for drama. An instigator. Quinn was a good one in the begginning. But now she is either whatever or really mellow towards MC. The thing is that diferent routes will have different stuff moving the plot foward... Sage has Jade, MaJo have their failling relatioship and, hopefully, the conclusion of the Maya's shit, Bella has herself, this may even be linked to the overall plot since no one knows basically anything about her and Jill...? I don't know, the maybe connection with with Lynette's family which can lead MC to meet some of his relatives? Tybalt is as good as an instigator as Dawe is.
But for the overall plot? There's the culprit that is trying to take the DIKs out, which is the main one here most probably. Then we have subplot like Stephen, the Drugs, maybe someone dying which I can feel coming for whatever reason, MC's blackout moments that can lead to something relevant. And then I don't know, I doubt the culprit is going to be the climax of the thing.
If DPC wants to kill someone, it won't be someone BIG in the plot like one of LIs or Derek (if DPC touchs mah man, I will find him). But he doesn't even needs to kill someone... I feel that if he makes that Neil has some sort of disease and/or ailment, this would be the perfect thing to move into the climax... something like cancer, alzheimer and so on. This would be my bet to move the story foward towards it's end actually, Neil IS the most important character in the game, since the game is about MC's life and without him, MC would've have crumbled already. (I don't consider the protagonist here, of course)