I've seen all the info about using SOCKS proxy for sharing internet, but what about setting up a true internet gateway through the iPhone? DHCP, DNS forwarding, can these be implemented in a way that a PC sees and uses the internet connection normally over Wifi ad-hoc without the proxy?

I don't want to be stuck using only FireFox for any internet activity. I'd like to be able to use VPN, Remote Desktop, E-Mail, SMB file access.

Any ideas?