Services normally have no way to be 'brought to foreground'. As soon as HFS runs as service, it's invisible to the user. Most programs that run as a service and have a GUI consist of actually two parts: The service part, and a 'frontend' for the service. The only part of the program communicating with the user is the frontend part. The frontend then controls the service. This may be the case even if there is only one .exe, the service continues to run even if you close the frontend part (e. g. when you log out).
AFAIK there is no way to access the HFS GUI as long as it's running as a service. Of cource you could edit the HFS.INI directly and have a commandline switch in HFS to reload the settings/VFS, but you can't edit the filesystem. You have to restart as a normal program to do that.
The account or user a service runs under primarily deals with permissions (access to network shares etc.), it does not allow that user to access the GUI.
MarkV