One thing that I think fuels the fire with the Ayaan/Zoya thing is that in the 1st or 2nd episode Ayaan makes that comment that Asad and him have similar likes so hopefully they like different girls as only a girl can come between them. However I think the show has come a long way from that comment mainly because Asad and Zoya have accepted their feelings for each other. If they had not then a Zoya/Ayaan track could make sense but I don't believe it does now. The show should focus on all the other stories and secrets that have not been shown and pursued. I think the clash between the brothers will happen when they go back to the gudiya factory raaz or reveal Gaffur's identity as Zoya's father or when they go back to looking for the person who tried to kill Dilshad. I think if the finger points to Razia then Humeira will be distressed and Ayaan will help her (or Razia could blackmail him as you mentioned) and Asad will be opposed... same thing with Gaffur and Rashid.
I am looking forward to seeing what happens when Zoya finds out who her family is... and also when Asad finds out who her family is.
For Nikhat and Imran... I'm not sure that would cause a rift with the brothers because I'm not sure Ayaan really wants Imran to be the groom since Imran doesn't support Nikhat anymore (in front of Haseena). The only thing there is that Shireen will emotionally blackmail him and freak out like she did last time (I really do not like how they have shown her lately). So in that case it's possible that Ayaan will try to save the marriage whereas Asad may try to stop it... but then I'm not sure Asad will try to stop it because he doesn't know if Imran is a bad person. Yes he had the relation with Tanveer and other than that Asad doesn't know anything.