Disabling cd does not do anything useful. Instead of:
cd /etc
ls
cat passwd
a user can just do:
ls /etc
cat /etc/passwd
And there is nothing that can be done with the restricted shells to stop that sort of thing.

The only thing that you could do is to have a seperate chrooted environment for each user. It will be rough setting that up. Unix really is not intended to be operated like that.