That's going to be a serious pain in the ass since each virtual server needs to have a "public" IP in order to have sites running on it. Otherwise you're stuck doing NAT and DNAT off internal IPs which you assign to the virtual server, which might (or might not) work.
As far as submits, doesn't matter much if they're on the same IP. Many shared hosts will have tons of domains on a single IP and that never caused issues with submits
I think, though, that if you really want to set up some newb-friendly hosting that you might as well just skip the VMware thing and set it up right on the server itself. lighttpd with the proper config can run PHP in a user-specific "jail", combined with Suhosin it shouldn't be the usual walking security hole, and given the proper FTP daemons you can limit each account to it's own directory.
If you want some more tips on setting it up, let me know, I used to be the sysadmin for a large webhosting company
