I have a happy update to this saga! It works!
This all has deviated quite a bit from the original post that kicked off this thread, so I'll write something more specific and detailed in the Shimano forum in the coming days.
Here's my attempt at keeping this update brief:
My AliExpress EP8 motor was originally designated for the Taiwanese market. Shimano specifically locks these down in such a way that the region can't "easily" be changed, 16 MPH speed limit and power output is restricted to 400W (from 500W).
So when my bike shop worked with Shimano USA Tech Support, and Shimano couldn't change the motor to the US region, they technically weren't blowing smoke.
I poked around at my options and landed on
eMax-Tuning who apparently are a dedicated crew of Shimano Steps enthusiasts in Germany.
The process is both complex yet simple — the main hurdle is reading through their very thorough instructions to understand what all needs to be done. Also, specifically for this motor I needed to be in possession of the Shimano PCE-02 Windows/USB interface cable, which I already own but otherwise is an additional expense. However, for many users eMax works over a Bluetooth connection. For my situation, it played out like this:
1. download the eMax miniMax software
2. send a screen shot to eMax-Tuning to make sure everything will work
3. PayPal eMax their fee for the license code specific to the drive unit's serial number
Now normally that might be it to make any changes, but for my TW-region motor it got slightly more technical. I'll save the gory details for a separate thread, but in a nutshell:
4. eMax provided a link to an earlier version of Shimano E-Tube software to install on my laptop
5. eMax provided a link to earlier motor firmware that I downloaded, unpacked, and inserted into a hidden Shimano directory
6. I connected the cable to the bike and opened this earlier version of E-Tube, which instantly prompted me to "update" (downgrade) the firmware in the motor
7. The installation went perfectly, just like a normal update, and took about a minute
8. using eMax's miniMax software, I was then able to select the US region (20 MPH speed limit) and modify my wheel size
At this point, I tested the bike and the speed limit had indeed been lifted. But my motor was still restricted to 400W. So...
9. I connected to the bike using the most current version of E-Tube, which detected I had been up to some unauthorized shenanigans and also advised me there was a software update available
10. I performed the software update as suggested, and this brought the motor back to the current firmware version (4.2.0)
11. switching back to the eMax software, I could confirm that I was now at the full 500W, was still at 20 MPH / US region, and could still freely adjust the wheel circumference
My only other mods were to (a) divide the correct wheel circumference by 1.6 (changed from 2190mm actual to 1370mm) and (b) change my display from MPH to Km/H. This gives me a 32 MPH assist limit but shows the correct speed readout on the display, just pretend that the Km/H is MPH and all is good!
I'll say this about eMax: The guy Markus who replied to my emails was super responsive. My initial inquiry was on a Sunday morning and he was back to me that day. Despite the time difference and a few back-and-forth emails, I got everything I needed to perform the update by the next day, Monday. I did take the extra time to read through everything thoroughly and download / install the necessary files while at my desk, but for the actual bike-connected-to-computer time, this was literally **minutes** and there were no false starts, everything worked exactly as it should have the first go, crazy and unexpectedly simple.
And back to the original subject of this email: I took the bike out today for its first real ride. The pushbutton Nexus shifting is working perfectly, about as well as I remember it working on the E6000 Raleigh it came off of. The EP8 motor is so much quieter and quite a bit torquier than the 6000-series, comparable to the Bosch Performance Line motors I've got on two other bikes. I've got to finish the build with the Jones bars, racks, fenders and lights, but for now it's finally a rideable bike that had previously been sitting, deconstructed, in a dusty corner for the past five years. I'll post a proper photo here once I've completed it.