Sid will be 100% angry and I hope he reminds Simran that re-marriage was not in their deal. The deal was to divorce Roshni not to get re-married to someone else. I also want Roshni to be there and Sid says it in a fit of rage or Roshni to overhear Sid talk about it. That way she will find out Sid's reason for divorcing her and that he is equally hurting because of it.
I hope though if it happens this way then I want Roshni for once to be there for Sid and help him through it. Roshni knows how Sid feels about his parents and she must know how much it is hurting him to have this type of relationship with Simran. I want Roshni to comfort him and console him as he has been doing from day 1.
If she does find out and does confront him about it then I want them along with the pro-SidNi in the show to plan this way:
Sid agrees to Simran and Kritika's marriage proposal.
Roshni also in front of them acts as if it does not bother her at all.
Marriage preperations begin but each ritual performed will be shown to KriSim that it happening between Sid and the chosen girl but in reality SidNi are getting remarried. The way Sid tricked DD and married Roshni instead of Krish this time everyone except KriSim will know about it.
It would be fun to watch how everyone helps SidNi get together again and trick KriSim. Trap them in their own plan.