Most plugin implementations write logging statements when the plugin gets initialized and destroyed (although not plugins do this, with in turn can be confusing).
The plugin manager can easily be modified to do this logging for every plugin. This reduces some boilerplate code while creating a more uniform log.
An additional improvement that should be introduced is logging the fact that all plugins have finished loading. Now, when a server starts that has a large amount of plugins, people have to guestimate, based on the absence of continued 'loading' messages.