To create such a manager the biggest problem is the following: How to convert from arbitrary layouts (as created by the authors) automatically to TDS (TeX Directory Standard) layout.
There is a partial solution which we use when pulling from CTAN into TeX Live, it is a script called
ctan2tds which knows a lot about many different packages and how to convert them to TDS layout. It even has an automatic mode if nothing special is specified. This automatic mode works quite well for simple packages, but no way for slightly involved packages.
Now for the super-tlmgr: There are several problems to be overcome:
- inclusion/extension of ctan2tds: this is probably the easiest part
- teach the super-tlmgr how to access a variety of sources (git, svn, zip, tar.gz, flat files, ...)
- make it platform-independent (good luck! I know how hard it is on Windows)
That said, it is not impossible. I envision a tlmgr extension that includes the ctan2tds code base, and in addition the user-mode patches so that one can install into arbitrary trees. The super-tlmgr would download the package from whatever source, try to run ctan2tds code on in, and put it into a temporary TDS folder and present the outcome to the user, offering to install or drop.
Of course, version checks, upgrades, etc etc might be problematic in this case.
Last thing: I don't think that I will ever have time to work on that. And there is another thing, namely that the ctan2tds code needs a rework and streamlining ...