SOLR-5556 a user can specify the class of the admin InfoHandler, but can't easily override the individual handlers that it provides (the PropertiesRequestHandler, LoggingHandler, ThreadDumpHandler, SystemInfoHandler).
Contrast this with say, the AdminHandlers, where a user can provide his/her own implementations of the underlying request handlers easily.
I've run into this limitation in the following setup: I use derived versions of the various AdminHandlers, and would like to use the same implementations for the InfoHandler. I can do this by deriving from InfoHandler, but then I'd need to duplicate the handleRequestBody dispatching code. That's doable, but not as nice as what the AdminHandlers provides.