That is be power draw at the outlet [0]. There is probably loss that occurs when drawing from an outlet that does not occur when drawing from the battery.
The NetBSD rumpkernel allows for running individual drivers in userspace, while UML and vkernel are both geared towards running full kernels. UML and vkernel both look pretty similar to me though.
You have misunderstood the article. It is not advocating for the return to single address space systems. It is advocating for potential alternatives to the linear address space model.
Here [1] is an operating system that I think fits under the description of what you were talking about
I think NilFS [0] fits your description, though it is somewhat obscure. It creates a checkpoint with every write, which can mounted after being turned into a snapshot.
Although the website seems to have not been updated in a while, it's mailing lists appear to be active. [1]
The response by one of the devs to the first problem is "In fact, the concerns on typing-friendliness always comes up in discussions about the GoboLinux tree. To that, I can only respond that, in a properly configured shell like the one that comes by default with GoboLinux, typing /Programs takes the exact same number of keystrokes as typing /usr: slash, lowercase p, Tab." [0]
The response to your second problem is that not all programs are well written, and they cannot afford to patch every poorly-written program.
As far as I can tell, the package manager handles dependencies, like most other package managers. Packages can declare dependencies on other packages, and the package manager installs each dependency only once globally.
[0] https://www.notebookcheck.net/Our-Test-Criteria.15394.0.html