I think I know why Viva was added as a character outside of plot reasons for many-ia reasons but 2 stick out more importantly to me Camila Cabello is the voice actor for Viva, prior to starting her solo career she was in a girl group called Fifth Harmony. Now do what you want and call me a skeptic but one of their big starts was covering Justin Timberlake's song "Mirrors" in a record of cover artists. This helped propel their careers, and as we all know, justin was in *NSYNC so like... cmon, how could she not. In TBT there is a strong references to boy bands specifically those around the 90's and early 2000's and while there are a lot of girl groups that could have also been mentioned this movie wanted to focus on Branch. But featuring a ex- girl group member does help advance this theme of single gender bands. The other reason, is because this movie focuses on Branch and his brothers. It is very male heavy, sure it's broken up with V&V but during their songs the only person to break up the male voice monotony was Poppy. And to draw a paraell to one of my other hyperfixations Newsies, they made Kathrine a whole new character just to provide contrast to the VERY VERY male heavy cast. She was supposed to give us a diffrent voice to hear outside of all the male voices providing a harmony that diverted you attention and enhanced the preformance. AND THIS IS EXACTLY WHAT VIVA DOES! During Better Place you hear Viva singing Backup along with Poppy, but whenever you hear Camila sing your thoughts are immedityly pulled towards it to contextualize what you heard. and on relistens this only adds and enhances, but it makes the whole song better for it. They made Poppy purposely quieter as Anna, no offense to her, has a very prominent voice that draws itself to you, and the reason why Poppy couldn't be singing Viva's part is because
Poppy is supposed to be singing with Branch, they are a family and its so important that they sing on time with eachother and 2. Poppy singing Viva's part just isn't emotionally reasonable on a story stand part either, Viva is new, we've had backstory on her but not as much as the other brothers whose prioity is to be singing the perfect family harmony. Viva is still an outcast to the audience, we don't quite under stand her and we wont until after the movie and after some thought.
You physically can't put Poppy in Viva's role so they had to make a new one, they couldn't make it another boy as that would add to the monotiny, so a female, and it must be a singer with a distinct enough voice to Anna that it wouldn't get confusing. So probably after alot of searching they landed on Camila and the rest is histroy
