Upgrade to the latest release. The latest release (6.7.1) has a feature (as of 6.6) that allows custom titles for any member of your board.
Basically you'd just open your control panel, click member management, enter the username, fill in the "title" you wish to use, then click submit; user will now have "Staff" or what have you under their name.
Also, there have been a large amount of security related upgrades and a large amount of features added since the 5.x series; the security upgrades alone would be a good reason imho.
