I recognize the Boost process is not well adapted to these kind of changes. If you want to change the Boost process please make a concrete proposal that takes into consideration this use case to this list.
I know you mean well, but I believe the problem is that anyone who has the political capital required to change the process isn't invested in changing it and everyone who is invested in changing it doesn't have the required political capital to change the process. If the founder of boost was given a billion dollars and decided that boost was the only thing worth working on and that modularization in the way Stephen proposes is important, I'm sure he could convince or otherwise spend political capital to get the change done with minimal coordination overhead and library maintainers would shrug and move on with their lives cause spending their political capital arguing with the founder of boost isn't worth it. But that situation isn't going to happen and even if I did make a proposal, it would be unlikely to be well received because I don't have the political history to understand what maintainers would agree to or not. It's simply not worth my time to try to fight political battles in boost when I could spend it doing something fun, like playing borderlands 2. Boost problems can only be solved by the current leaders of boost recognizing issues and trying to solve them using their political capital and time. If none of the current leaders are interested in defining a policy which is friendly to these types of changes, then it will never happen, unless someone has way too much time on their hands and wants to waste tons of it gaining enough influence that they can change things. And that's just hard, even with an arbitrary amount of time.