> Sure, these three are life long collaborators and definitely split the
> work, but Marco has to be the captain on the boat.

This is the best analogy. It's common knowledge that all composers use ghostwriters - it's an absolute necessity when things come down to a time crunch. There are times when it's just physically impossible for a single composer to write however many minutes of music are needed in the time required by the film's post-production schedule, and orchestrate it properly, especially when the film is being re-edited at the same time. EVERY composer has needed to do it at some point in their career. EVERY SINGLE ONE. No exceptions.

What usually tends to happen is that the lead composer - be it Beltrami or whoever else - will be the one to decide on the tone and orchestration of the piece, the lead composer will decide on the spotting for the length of the cue, the lead composer will be the link between the director/producer and the music team, and the lead composer will sometimes come up with a suite of themes which are to be used throughout the score (as Zimmer does). But, depending on the time crunch, it's very common for other composers to actually WRITE the cues, using those criteria as a framework. I was physically in the room with Dominic Lewis when he was writing some music for Kung Fu Panda 2.

So, for Beltrami, you can still focus your positive or negative energy on him about the score, because he was still the one who decided on the TONE and APPROACH for the score, even if Trumpp or Roberts or whoever wrote the actual NOTES.