How do you make people collaborate, in a scenario like that, where each person has 1-2 projects of their own? How do you prevent these projects from becoming “niches”, and expand in complexity to take the entire time of each said developer?
The way to go about a collaboration depends on the reason for the collaboration, and why it's a better idea than not collaborating. I don't think there's a general answer to how you "make" people collaborate.
The question about project scope and resource allocation is also hard to answer in a general way, as I'm not sure why it would be harder in the world I'm suggesting.
