It's been a while since I really tried to answer a question from a completely serious POV, so here goes:
The temptation to help an artist that one thinks is worth the trouble is often brought back to reality when egos collide. I think that in your case you have more talent than you probably give yourself credit for and this gives you bargaining power if you choose to use it.
Before you donate your time because you believe in something, perhaps it is best to hypothesize about what will happen when there are creative differences. This way, you can get artists to show their hand before you start giving up your valuable time and energy only to find out later that unless you are their glorified monkey, they are going to think you have cheated them of their vision.
What you are betting on in most cases is just getting paid, if there is a success (realistically low odds). At least the days of them taking it to a label and redoing it so you get nothing are about over, except in the most rare of circumstances, but this is only a peripheral point.
Are the people worth giving of yourself? Talent is not the question either. Character is what is really what is on the scales when we donate ourselves to someone's vision. If you don't think they respect your potential contribution, then send them along, regardless of their talent. Lots of assholes have talent, and I don't want to subject myself to assholes, regardless of the monetary or fame potential. They are not worth it.
