There are two things you hear in your first deployment of a Publishing Site:
- XHTML validation
- Full URL customization
Although there were some commercial solutions (I remember RAPID having developed an HTTPModule, buti t seems they had deprecated it), I saw public information in order to implement or configure this behaviour.
Although it is not trivial, as the product is huge, and testing may have no end; it seems feasible.
Searching for URL Rewriting components, you may find ScottGu post talking about:
And for those 2 solutions, you may find feedback after being used in MOSS:
The nice finding of Daniel Gonzalez was the way some webparts handle the URL (reusing at the client document.location as a valid url)
So my personal advice would be to be careful to talk about a full solution for URL Rewriting, and instead talk about a specific solution in a managed scenario: "Anonymous publishing site with managed webparts"