I used to have several Eclipse installations, and workspaces, with optimized set of plugins for a particular job - for PDE development, for Scala, for experimental plugins, modeling tools, JBoss and Spring integration etc.
I like the convenience that nowadays all plugins are available in any workspace but also with every installation. Too many plugins still cause Eclipse to start slower, experimental plugins tends to be buggy and cause issues even when they are not actively used, polluting menus etc..
With newer Eclipse versions trick with multiple installations cannot be used anymore. The plugins are shared across all installations by default. They are installed in "pool", a directory outside installation, in something resembling Maven local repository.
Eclipse now has Oomph, P2 Agents, P2 Bundle Pools, Oomph (?) profiles. Can I use any of those to restrict number of available plugins?