Right now the process of deleting/purging RHQ agent plugins contains various periods of time during which the user has to wait for the process to complete. There are no/few visual clues that you are in one of these wiat period or when a given period completes. 

In general it may be worthwhile revisiting the plugin deployment model to see if a process redesign that removes these waiting periods is a better option than providing more visual clues to the periods themselves.