using "/blog" as a site address

I have run into a very frustrating problem whereas the multisite version of WP does not allow users to create a networked site with the /blog site address. I’ve read the reasoning as to why this is the case in the install instructions but the problem I have is a client already has her business blog vis a vis a wordpress install set up as domainanme.com/blog.

she wants to continue using that path so that internal links on the existing site and incoming links won’t be broken when transferring the content from her old host over to the new host. But if I can’t create a site name with “/blog” then all of that is out the window.

How do I go about getting rid of this restriction and the subsequent”The following words are reserved for use by WordPress functions and cannot be used as blog names: page, comments, blog, files, feed” error message?

I don’t care if it requires a hack, I need this to work and am VERY disappointing that WP didn’t find a solution for this earlier since so many people have set their blog up in this way over the years.

Thanks in advance to anyone who can help out!