Duets - If songwriters are writing in groups for most of the season, why not have them write duets? The duets don't necessarily have to fall under the genre of love songs and it would show that songwriters understood how to write for two different voices with different emotions. For example, Sonyae's music was quintessentially Sonyae, so I'm not sure if she would have been able to think of a duet by herself.
An Unconventional Challenge - Shows like Top Chef and Project Runway have the ability to create an unconventional material challenge. This could translate to Platinum Hit in so many different fashions that I'm surprised they didn't have anything too hard for the contestants. One example would be unconventional instrument challenges; could Scotty create magic with only a kazoo? Another would be if they were all forced to use the same exact backing track or same hook. Finally, make the songwriters write a children's song aimed at a Nick Jr. toddler audience and judged by the little kids and their families. Contestants need to push harder so that they can evolve as songwriters.
A Live Band - Similar to having a different singer, the use of the live band in the final episode changed the dynamic of the final three songs completely. Most of the contestants in the first season produced songs with really generic backing tracks; that would have changed if they had the ability to work with a full band. It would be interesting if a whole band competed instead of individuals because of the dynamic.
I hope that Platinum Hit gets a second chance on Bravo because there were some amazing songs created through the show and it was a concept that could pick up. I'll accept that Jewel's camera style was a bit wooden if we could get Kara to be more involved with the contestants.