When you say you only use one FTP user, do you mean you yourself have only one on your account, or do you mean that you use one, but you have created others for one purpose or another? If I recall correctly, unless you have other FTP users with shell access, you probably don't have anything to worry about; if you have only one FTP user, you definitely have nothing to worry about as far as group permissions are concerned. (Still need to worry about the rest of them, though!)
I doubt support would change your directories' groups to dhapache, particularly because you would want it to apply to all new directories as well, and you wouldn't be able to set up your own cronjob if the group were dhapache. What you can do, assuming you still think you need this, is follow the instructions on setting Unix groups.
Very little to do with either emus or farmers!