OS X Server 10.10 and uid 500

I've got OS X 10.10 Server installation (mac mini). I have couple users and one of the users inherited uid 500. uid 500 considered service uid in OS X and is not being shown in Server application, so I can't add user to the groups easy via GUI. Since I have huge park of linux servers, where uid 500 is user-assignable, it is easier to look for workaround for OS X, rather change uid on all servers.

Is it possible to tell OS X or Server application, that first local user is 500 and last service uid is 499?