Different Themes/Plugins for different Users


I want to find a way to give different user different default plugins/themes (in particular I want to have four different groupings). The idea is that I give one group one link and when they register they have access to one group of plugins/themes. Other groups will have different log-in links and they will have access to different groups of plugins/themes.

Any ideas on how I can do this?

Thanks and be well,