Some of your comments indicate you’re still hoping to get rid of project maintainers, which is unrealistic. GNOME is a big collection of small projects, and teams with a large scope and perspective are just not a better way of working on small projects. I see only two possible ways that ends: (a) we’ll continue to have de facto maintainers and everything operates same as before, except without any way to formally indicate who the maintainer is, which is not an improvement; or (b) we take “no maintainers” seriously until chaos ensues and eventually we change our minds and bring back maintainers.
But I see your proposal does not directly call for replacing maintainers. Forming some higher-level teams seems fine. I don’t know how well they’ll work, but why not give it a try? Even if only some of the teams are successful, that’s a win. Giving those teams formal power, including power to overrule maintainers, also seems fine. (Our fiefdoms should be “softer.” Collaborating well together is more important than exerting absolute authority over particular components.) Creating a steering committee to relieve release team and design team from serving that role also seems like a clear improvement. I suppose my suggestion is: try everything you’re saying, but layer it all one level above maintainers rather than eliminating maintainers entirely.
Exception: I think it’s perfectly fine for the maintainer of a particular project to be a team rather than a list of individuals. But this will probably only work well for a few GNOME projects, not for most of them. And the teams would likely have to be of narrower scope than you propose here. E.g. a Platform team is probably not a good fit maintaining the entire development platform, because the development platform is huge; you might be interested in GTK and Pango, but maybe not in libsoup or libgdata. An OS team is probably not a good fit for maintaining the entire OS. (Higher-level teams could certainly oversee lower-level teams and maintainers, but now things are starting to feel pretty complicated. Then again, that might be OK since we can evolve as we go; no need to get everything perfect from the beginning.)