Clinet interested in multiple front-ends to test functionality

I have a potential client who delivered a list of must-have functionality along with a wish list. #1 on the wish list was the ability to create two different front-ends for the same site using a different navigation scheme. The idea is that this could be set up randomly, so different users would have a 50-50 shot of seeing either possibility, and then the client could review data on which navigation scheme was more successful. I know I can create multiple menus and switch them for analytics examples, but does anyone have any idea of clients' request is doable?

Thanks much for your time!