The instant torque on the i3 means it is easier to abuse the tires than with more conventional engines that require the engine to spin up a bit before it has the torque to affect tire life much. It's so much fun with the i3, and quiet while doing it.
I expect in the next year or so, other manufacturers might come out with suitable low-rolling resistance tires designed for the i3. The only other manufacturer that makes one specifically for the i3 I've found is Nokian, but that is a winter tire, not an all-season. As more and more i3s are sold, and they start to need replacement tires, others will be more inclined to go to the expense of tooling up for a new tire size with the desired characteristics. What complicates it somewhat is that there are four different ones, two each in 19 and 20" sizes, which limits the market. BMW, and many vehicle manufacturers, like to have more than one source of tires...it helps the competition and keeps prices down, so there might be something in the works, but that is a guess.
The UTQG for the stock tires is 440, which isn't horrible. Some of the performance tires are only like 200. Make sure you keep your tire pressure at the design levels.
Sorry, doesn't help when you need them now, though!