Exciting to see!
Is this an omnidirectional one sector site, or does the 2x20 watt imply it's a two sector design?
The design doesn't look bad. I can see it fitting on many pre-existing wooden power/telephone polls.
That antenna appears omnidirection (maybe pseudo-omni), but a panel antenna could be used instead depending on the coverage target.
2x20 means the radio has two ports capable of 20 W each. Each B41 channel needs to transmit and receive on both ports to create the two parallel paths necessary for MIMO. Typically you deploy one radio per sector. 20 W leaves room for 2 or 3 CA using 10 or 6.667 watts per channel respectively assuming the radio supports more than a 20 MHz bandwidth and the rest of the system supports CA (modem and controller). I would have to image Sprint required at least 2 CA support.
For reference the macro site B41 radios are 8x20 watts. They have eight ports to allow beam forming. Also 8 ports allows 8 branch receive diversity which improves the UL performance. UL is typically what limits a cell's size. This is especially important in TDD because you are not receiving all of the time (sometimes you are transmitting) so the average received power is lower than FDD for a given frequency. FDD typically uses 4 branch receive diversity for B25 (B26 uses 2 branch) so there is a 3 dB (twice as much) boost to the UL link budget using 8 branch Rx vs. 4 branch. You still have higher propagation losses at 2500 MHz versus 1900 MHz, but you make 3 dB of that back by using twice an many ports to receive the signal.
These mini-macros only have 2 ports (8 cut in half twice) so right there you have a 6 dB reduction in the link budget vs. a macro site 2.5 GHZ TDD.
The existing ALU (Nokia) B25 small cells (MCO) use a 2x1W transmitter configuration. You can use technologies like enhanced inter-cell interference coordination (eICIC) to extend the footprint of the small cell, but the MCO is still limited, and you only have 5 MHz FDD on an MCO. These 2x20W B41 mini-macros should be better in almost every way.
If using B41 for BH you would need to use resources of a nearby macro. However, in many cases B41 macros might not be highly loaded because of limitations of the 2.5 GHz frequency so these mini-macors can be use the extend the range. Tim has an excellent article on this. The best BH is fiber, but microwave can be cheaper, and UE relay is cheap and fast to deploy. You could come back and add fiber BH later as capacity needs grow.
I've heard rumors of Nokia having these, nice to see one deployed.