I have a 1940's undetermined brand Cruiser that is a sexy beast. It's outfitted with a front rack with springed grasper, a large rear luggage carrier and folding side baskets. I use it for groceries, transportation of large goods and just taking a nice sunday ride. However, I am less likely to take it for a spin due to it being on the slow side. (I'm more accustomed to my racing bike where I fly everywhere from 24 mph to 32 mph)

I've been thinking about it, and I was wondering if it was possible to outfit this bike with a Sturmey Archer 3-speed or Shimano Nexus 8-speed rear hub to add some speed and ease of getting up large hills when fully loaded. It has a coaster brake which I adore and am also wondering if that would be affected by the changed hub. It's great for the rainy weather that is very imminent here in California.

Any input would be greatly appreciated! And here's a picture of meh baby;