Setting up subdomains to ftp dirs

I am hosting a ftp server for some of our sites users. When you setup a new ftp user it always sets up their home directory at /home/username. This is fine, but I need a way to redirect a HTTP subdomain at these dirs so the users can share the files. Normally, I would jsut go edit the httpd.conf and add some virtual hosts for these accounts, but that isnt possible in shared hosting environments. I cant setup a symlink either because of course access to /home is restricted.

How would I go about setting this up?

You can setup symlinks and use SFTP, or create a normal ftp account and share the login details.

So I cant have the functionality that some users can upload files and others can download these files?

Use SFTP, symlinks and Unix Groups for the uploaders.

Remap the shared folder to your domain and give the "download only" people the http link.