So i understand correctly: Mount points will be still possible for subdomains and aliasses, you can offer another content on them ? The only change is, that you can't define them yourself?
no problem for me - a symlink will do the rest, but if you're going to delete the option to make an second webspace for aliasses and subdomains i will stand on the rc forever
please remember users that are using symlinks for patching: what will happen, when you use a "standard hosting" on a subdomain, but htdocs inside it is symlinked to another directory?