Well, seeing as how BB11 was a massive success (that was built around the pre-existing Shilpa/Vikas issue) and how BB12 was a massive failure (that wasn't built around an existing rivalry), I definitely think that the SidRa focus was scripted. But its not exactly scripted as in the traditional sense. I just think they were given general pointers on how the season would go. Sid would have Aarti supporting him and Rash would have Arhaan in the house for support. This sort of got proved when Salman exposed the fact that Rashmi was offered BB many times before and only now agreed, one of the reasons being the spotlight Arhaan would get. Not only was Arhaan shown as a "surprise" wildcard, but Rashmi even straight up acted like Arhaan was her friend and their love was slowly blossoming. BB kicked Arhaan out, he went to all media houses and said there was going to be a big love story, and then upon his return he immediately started with the ring wasting no time. That entire thing has been exposed as being fake. Now, if Arhaan's kid and all that shit was planned IDK but I have a feeling it was since Rashmi seemed to have planned the rest of it plus she seemed to get over something so major pretty quickly.
If Rashmi was given this treatment, then I'm 100% sure so was Shukla. Because these were planned to be the 'leads' of the show. The concept only works when both of them are brought together, since fans liked their chemistry. Even after all that has happened, you still see some people shipping SidRa lol, so clearly they are popular. Was aisi ladki etc. planned? I doubt it, cus Shukla REALLLLLY stooped down to a disgusting level in all that, and even with Salman's whitewashing, he's lost a ton of fans. But I do think they planned to have a fight in the middle and then again become cordial around the end. This sort of explains why Rashmi is suddenly starting to tolerate Shukla (and vice-versa) even though she's spending all day with Asim who genuinely doesn't like him. So I'm sure Shukla ka bhee koi guarantees hai contract mein, maybe sure-shot finalist or something. No wonder why he can do as much dhakka mukki and be as ghatiya as he wants!
Yeh sab mein Asim and Sana were the surprise packages. Asim because his story is genuinely very relatable and believable - that of a younger friend/brother type character who got sick of being insulted by his mentor figure. Plus, he's really good at tasks, has a great overall personality, and doesn't back down from anybody (which is crucial to this season's chhapar-faad TRP since without Asim the whole house would be full of Shuklis and there would be no feeling of competition). I think Sana connected purely because of her personality, and her good looks (Asim too, to some extent). When the season got extended, VG showed up out of nowhere and desperately started filling Sid and Sana's ears about SidNaaz. Us time pe ship thah thoda but itnaaaa nahee thah (baap-beti bolte the log), but VG really pushed it. I remember at one point he even grabbed Sana and dragged her to bed with Sid. 🤢 So I guess yes scripted thah kahee na kahee but I personally think Sana wasn't made aware. They just kinda brainwashed her by having a the guests, VG, even the rigged comedy club crowd support SidNaaz.