Sounds good in theory and I don't disagree with what you are getting at but they would have to change the laws in which performers/producers get paid on royalties if that were the case.
Actually, rap is the strange one when it comes to law.
Traditional setup is songwriter, producer and performer - producer and songwriters tend to get 50% cut of the royalties each, while performers are more likely to be paid a one off. Producers are generally not songwriters though. I'll use the examples of Blur and The Smashing Pumpkins to demonstrate.
SP - Billy Corgan, the main songwriter, has sole credit for writing almost all of their songs. That means that all royalties from the sale or play of songs written would go to both him and his various producers. Even if the bassist or the drummer in the band came up with their own rhythm/basslines, they would not get writing credit because the original idea for the song, the lyrics and the melody come from Billy Corgan.
Blur - All music is credited to Blur and all lyrics are credited to Damon Albarn. There are 4 members of the band, but credit is split 5 ways - likely this meant that the producer got 50% of royalties while Albarn got 20% and the rest got 10% each. This is a bit closer to the rap method, but it's relatively rare (I think Pink Floyd was a major band to take this approach).
So what you generally have is a words/music split - this is actually how Dizzee Rascal used to work when he still self-produced. He took sole credit for words, he and Cage (his manager and producer) took combined credit for music, and Cage was considered the 'producer'.
Rap is completely different - the producer is often not involved in the recording process, but gets an additional writing credit for coming up with the music. Now, unless the producer is an idiot and forfeits royalties for a one-off payment (which a lot of producers have done in the past) he would get a substantial cut of royalties because he would be dipping into the writing side as well as the producing side. This is what needs to change, in my opinion. We need to go back to the view that a producer is not a producer but a beatmaker - give him writing royalties if necessary, but if he's not there to influence the direction of a song or at the very least give performers some guidance, he's not a producer.
