Not that I am aware of. . You can specify the “home” directory of each “domain” easily enough, but user directories are established by DreaHost at user creation time.
Looking at your earlier post(s), while I am not willing to say what you are proposing cannot be done, doing it the way your describe it with FTP would be, at best, a complicated process of custom user group creation and permission settings, likely involving cron scripts to modify permissions (see this wiki article).
Why don’t you just employ a “filemanager” type script to handle the “shared” aspects of you setup? This allows finer control, leave all files owned by “your user” (DreamHost uses suexec), and should be far more secure.
You might also consider employing remapping sub-dirs, but IMO ustilizing a script or scripts is a better approach to take.