Oh well, everyone is a critic. I'll take my shots. He picked a good frame to build on, with Dahon, Some of these no-name folders, you gotta think about frame integrity, especially with mid drive speeds. I heard those brakes howling. I don't know much about Dahons, but I think if he's willing to get a 100mm front wheel (Dahon is 82mm?), he could upgrade to a new fork with disk brake up front.
Maybe a black stem for the BMX bars, instead of silver. He's got a super low riding position. I need a lot more leg extension than that, because I still like pedaling my ebikes.
Always tough to place a battery on a folder conversion and maintain looks. In this case, it's not clear the bike can still fold, unless he only used the two water bottle rivnuts to hold the battery cradle. I only fold mine after I've removed the battery, so I have my battery locked down at both ends, preventing a fold when mounted.
I wouldn't have used a friction shifter. That's funny. I like the Shimano trigger shifters. If he thinks mounting a speed sensor is a big deal on a 20", he should try it on a fat tire bike where the distance from the frame chainstay to the spoke is 3X longer.
Good color. I am tired of black bikes.