Let's say every plugin author could add an exported function to the library (dll or wfx), InstallPlugin, for example. In this function, the author write the code to automatically install the plugin to Total Commander, for example, modifying the wincmd.ini file...
Then we only need a program that unpacks the plugin archive with all it's contents to a temporary folder, and calls the InstallPlugin function of the plugin.
Well, this combined with a Plugin Repository could be very useful, but that's just a dream...

P.S: I must excuse for my english today more than other days, it's worse than never...