The problem with an image based ecosystem that I see is that you are inevitably pushed towards using tools that live within that image. Now granted, those tools are able to be very powerful because they leverage and interact with the image itself. But the community contributing to that ecosystem is far smaller than the communities contributing to filesystem based tools.
The result is that people who are considering coming into the system, have to start with abandoning their familiar toolchain. And for all of the technical advantages of the new toolchain, the much smaller contributor base creates a worse is better situation. While the file-based system has fundamental technical limitations, the size of the ecosystem results in faster overall development, and eventually a superior system.