The concept behind this looks horribly unfit for a webapp, as application and presentation are coupled pretty tightly. Is this an absolutely required feature?
Well, that makes a bit more sense, but not a lot. Spreading over two servers is not an issue if the RDBMS of your choice is network-capable (i.e. it speaks tcp/ip or a comparable protocol). However, it is problematic to have presentation and application really separated as in webapps, the application is sending the entire presentational data to the client in order to be interpreted and rendered there. If I were you, I’d get back to whoever wrote that spec and demand clarification. It looks a lot like s/he hasn’t got a lot of experience with designing web applications.
If you really need more security (or the impression of it), consider getting a web application firewall such as phpids or mod_security.