Replace root site with subdirectory site in network?

Apologies in advance if I’m missing something obvious. I setup a network of sites in 3.0.1 using subdirectories. I built out a site for a client and now the client wants the site I’ve built to be on the root domain.

Client: “Yeah, make http://www.domain.com/oursite/ just http://www.domain.com!”

Given that I’m using the “network” feature in 3.0.1, what’s the best approach to do this? I don’t think I can simply redirect the root to the subdirectory using .htaccess.

Any insight appreciated. In a worst case scenario, I guess I could wipe and reinstall the site as a root level WordPress install without a network feature, but I suspect the client will want other sites in the future.

Best,
E.