well if I type 192.168.0.1 I will connect to a machine on my network, not yours. Internet routers will not route those numbers, they are for LANs only.
You really need to have a valid ip address. The other thing is port forwarding, you could forward the port that people will conect to on the main machine to the other machine. Most people use this method for internal webservers, but not having the router a webserver too.
I think what I would do here if the one machine can't simply do everything is to setup the other machine to share the website over nfs, mount it on the main server machine and point the virtualhost to it. That would use the disk space of the second machine and the webserver of the first.
There could be some other solution that I'm not aware of, is there a particular reason why the first machine can't do everything?
here's my question. if the forwarding is just an index.php file, won't that mean that requests for otherbox.mydomain.com/someotherpage.htm will fail? any clever way around that?
not sure if there's another way around the port forwarding, if the port is forwarded though then any request on that port would go to the machine. However requests on port 80 would go to the main server. they would need to be requesting all pages and files on the forwarded port.
The initial request could be 0n port 80 because it would not include a filename, just the domain name.
all other links would need to be structured like this
which is not real pretty but could be done with all of your links
another thing you may be able to do is to have some php script that would catch every request and rewrite each header.