In reading this thread it is quite apparent that with the stock Bafang being wound for torque as it is that getting it to go faster than it's parameters set by Rad, which has to be conscious of the legal requirements for sale here. While I can appreciate the need for speed that some are after and all the options mentioned here like displays, controllers swaps etc. are not going to make the motor any faster due to this limitation.
The loss in efficiency going to the upper end of a motors output is a big factor here. The faster you go the further you won't. As the stock battery appears to be an 11.46ah and the fact that it is probably on the lower end of the mAh spectrum per cell and the battery being the heart of an eBike there are limitations there also in regards to squeezing the most speed available out of the bikes. At 550wh at the 30wh/mi I would nominally predict that going the extra mph's consistently would only provide a range of 18-20 miles at best. In other words the key to having the most motor power is the battery that will supply that. And going to 52v is one way as suggested but while that adds some watt hours to the equation suggesting more range it is my experience as a 52v user that also has a 48v system on similar bikes that both are about as efficient as the other range wise with a slight nod on the fresh off the charge oomph you get with the 52v.
Here is a spread sheet I worked out that illustrates what the emerging 21700 cells can provide in comparison to the 18650 cells currently in use on the Rad lineup and others in the 1500-$2000 price range.
This is based on a 15ah rating but still provides the necessary info on how a better cell can aid in the overall performance of a battery, which in turn translates into better overall performance of the motor. A higher discharge rate will allow for more peak power but also if used conservatively will draw less power creating more range per charge. Also the higher charge rate possible would mean with the right charger the option to charge at the highest rate of 7A which would bring a battery at 20% charge to an 85% charge over a long lunch break. The last 15% would take longer as proper charge cycling demands that the last amount be fed in more slowly. But even still as it is recommended for best battery life to only charge to 85% and the fact that is still bringing the battery up to over 12ah's a quick charge now and then is well within the range of proper battery management using the new cell structure.
At this time the availability of such a battery as described in the second column is just figures on the screen. In order to go to the new battery, if developed, however would be a simple as matching the lead connectors and plugging it in to your Rad bike. This is made easy by the open source nature that Rad subscribes to as there are no proprietary communications within the BMS/conrtoller interface such as found on the big manufacturers 36v models. Due to this they are subject to their systems batteries only.
Going forward the availability of such a battery, given that you are happy with the bike overall and that batteries do degrade over time, if you are considering performance upgrades a strong battery seems to be the most simple way to achieve performance. A caveat here that the battery in question would certainly cost more than a stock one from Rad and the charger necessary to achieve maximum charge rate is also going to add cost. The way I see it folks that have Rad's have gotten them as they represent a price point that at the entry level is hard to beat, especially as they are on top of their customer relations it seems that other similar spin offs seem to lack.
So are the Rad bikes just a starter bike that once you have had a good taste of what an eBike can do for you and you want something more powerful you have to look elsewhere, as in a new bike purchase, or does the possibility of a battery upgrade alone that would enhance your current bikes performance and range with the possibility of decreased charge times and the fact that you are perfectly happy with the bike itself make sense? Time will tell I guess.