Is your feature request related to a problem? Please describe.
A couple years ago I tried showing Blender Launcher to someone and they were sad it also doesn't handle the Blender configuration as well. I can see how this is useful, for example different sets of enabled addons. Every blender version (since 2.50 at least) have used these environment variables to handle user configuration:

 $BLENDER_USER_CONFIG     Directory for user configuration files (ex. userpref.blend) .
 $BLENDER_USER_SCRIPTS    Directory for user scripts (such as addons).
 $BLENDER_USER_DATAFILES  Directory for user data files (icons, translations, ..). 

Describe the solution you'd like

A configuration handling system where you can assign different blender builds to a specific config / script / datafile directory or all three. In terms of execution, all this should require is either changing these environment variables before running Blender, or changing them in the same command as running blender.

Describe alternatives you've considered

Symlinking different versions of the Blender user config folder to the default config directory. Not ideal.