As it turns out, somebody already tried a Patterson Metropolis + Shimano Nexus 8 combo three years ago:

The Hub Bike Co-Op Blog: Let The Patterson Transmission Enhance Your Commute

I contacted the coop to ask if that bike is still around and if they still like that combo. I got this email reply:

One of our mechanics rocks this set-up, but usually doesn't start riding it regularly until winter time. He's been using it for at least two seasons (maybe 3) and continues to love it.

I'm guessing it's the same bike that was shown in the blog, which says something good about the durability of the Patterson.