It can happen, but not just for the heck of it, something worthwhile should come out of it. Something like this would be alright ---
Siddhi agrees to marry Abhay thinking Kunal has moved on and asked her to stay away from him and Richa so she needs to move on in life too for her son, Kunal finds out about the marriage and out of jealousy jumps at Richa's two day offer and agrees to marry her. Kunal lies to Siddhi about remarrying Richa because it is their 10th wedding anniversary or something, Siddhi taunts Kunal saying now she will never interfere in his and Richa's life as she is marrying Abhay. Both Kunal and Siddhi are hopping mad to know that each of them is marrying someone else. Continuation of bullying/harassing/taunting/cornering each other at the office for no rhyme or reason except jealousy. A week before the weddings, Abhay sends Kunal and Siddhi out of town for some case. Some emotional hullabaloo happens during the trip and they end up doing the deed. They return to Mumbai and feel guilty, but NOT because of what transpired between them but because they feel they are cheating on Abhay and Richa after what occurred. Both realize what they are doing is messed up and makes no sense and they cannot think of moving on from each other, both back out of their respective weddings in time. After this psycho queen Richa blows off her head and probably says something that gets Kunal suspicious and then gold medalist uses his brain to work out the rest of the story.
So, the ultimate positive being that it ends the horror of Kunal-Richa and Abhay-Siddhi weddings.
