20mph instead of 15mph would make them perfect for a lot of people’s commutes.
15mph is fine (IMO), the whole point is it’s not supposed to be faster than a normal bike! If it was faster then the infrastructure becomes unsuitable for them (cycle paths with wobbling toddlers on balance bikes).
Then the only issue would be insurance, I assume pedalsure or similar wouldn’t cover a de-restricted e-bike/
I’m sure someone would insure it if you rang around custom motorbike insurers.
TBH though, why would you not just get this? By the time you’ve jumped through all the hoops it’s probably cheaper (the 2017 version is discounted to be cheaper than a lot of e-bikes!)