About Dire Straits, besides the MFN intro idea, who wrote the intro, etc, there are songs that we know must had more than contributions.
For example, we know TR was developed by MK and Alan, hand by hand, during the soundchecks of the On Location tour, it's MK song but, where Alan's contributions ends as such and develope into co-composing? A grey line.
Also, we know that Paul Franklin was playing some steel guitar warm up licks, Jeff Porcaro followed him, and MK liked so much that he included that in "Calling Elvis". Does it means that Franklin and Porcaro deserve credits for creating one of the main rythmic parts of the song? Or it was just a contribution?
I'm sure that there are lot of more examples, as Quizzy mentioned the Richard Bennett intro for "Rüdiger".
Hmmmmm, a good example would be Larry Knechtel writing an amazing, astonishingly good piano arrangement for “Bridge Over Troubled Water”. I mean, the demo Paul Simon did is completely different, it's not the same song at all, and yet, no credits for Larry. Because I think what we have here is the situation of a well-established songwriter.
You can do anything for such a songwriter but he’s not going to provide you with any credits regardless of your input. Because I think he understands that it’s a fair game. He gives you the platform, advertise you if you want, and it’s your job to do something with it next. Either you’ll grow and do even more, or cry like a baby asking for credits, it’s your choice.