Just saw the episode and I have to say there is no way Viaan went through with the ONS without being attracted to her. Maybe they didn't show it frame by frame in the show initially but it seems like he already had feelings for her because I don't see why else he would choose to go ahead with it. Even when he made the proposal and when Katha at first rejected it and left his room he felt some kind of a relief so he most likely was attracted to her. Also, he definitely doesn't give off creep vibes unlike in OG despite putting forth the proposal and the ONS happening so I still can't blame him entirely for the ONS even though he was wrong at making such an offer in the first place and has no right to test any women let alone Katha. Perhaps his childhood and past really messed with his mind after being stunned with Katha's acceptance to the proposal. But that means he really has to feel the guilt once he finds out the truth about why Katha wanted the money.
Also, I've had a conversation with my friends about this show and it might be a generational/cultural difference but people have told me that to them ONS would not be that big of a deal when it comes to saving your own child's life and especially if they have limited time then they wouldn't look at exhausting all the options rather it would be more important to see what would get them the money in the quickest way possible. Just thought it was an interesting viewpoint and obviously everyone grows up with different values/morals/ethics and family background so some may or may not be comfortable with ONS even in dire situations. In this case katha obviously could have taken the rival company's offer or even called them back but her desperation grew to the max when she was pushed to the edge after seeing her son in the hospital which made her focus more on the money part rather than the mode of how she was going to attain that money.