What if Asad and Zoya are married and by a twist of fate Asad ends up sleeping with tanveer in a drugged up state. He will feel guilty as hell but echoing Zoe's "tau umbra" promise she will stand by Asad. Ajmer may not be so much a reunion as it is tanveer being completely exposed and Asad possibly echoing his feelings. Post Ajmer life maybe seemingly good but it is entirely possibly that Asad will feel incredibly guilty and Zoe despite her love and understanding of the situation experiences a deep sense of betrayal and pain. Asad being the dogooder that he is may release Zoe from her marriage to him because be can't bear the pain she is in and miscalculated that for her being away from him maybe greater pain. We now have two characters who are in lob and in immense pain with the added angle of Zoes feeling of betrayal because Asad ends their marriage with no explanation.
At the same time we have humeira and Ayaan imploding. Ayaan, who by this time will be deeply in love with humeira, will be shattered. Despite many attempts to reconcile humeira may not be very forgiving and she shouldn't be. Zoya and Ayaan now both hurting could develop a deep friendship and maybe to find solace and mitigate loneliness marry each other. Note they are NOT in love but there is mutual respect and appreciation for each other. Should this happen Asad an humeira will also feel a sense of betrayal. Now we have a drama filled with angst between our four love birds. Eventually, manipulations and mysteries will be revealed bringing to fore how they were victims of a grand plan. ZoYaan mutually agree to divorce and the healing process for both AsYa and humyaan begins.
Note: I have tried come up with a halala theory without it getting messy. If zoYaan were to happen I would rather it be this way where everyone's true feelings are known, all characters are sympathetic and no one goes against their principles.