When I run a job or create a schedule in FME Server, the workspace parameters are populated as they were when the workspace was saved in Desktop. When I want to change such a 'default parameter' (eg. path changes, email changes, carre centre openings/closes, etc) the update requires the cycle of download the workspace - change it - re-upload. The same with private parameters (that I set to private because I don't want users to change it). I also use these default values to make the workspace URLs short, preferably no URL parameters at all (so users don't need to bother with things, just click the link)
The overriding/management of these 'default' parameters (all private, public and FME Server related ones) in FME Server would be really handy.
A nice extra would be to set different defaults per service or even per security groups. Eg. download service fail notifications could come to me and streaming service fails to web team, too.