Hello josh222,
thank you for sharing, your experiences with U-Boot mode.
I've tried the USB Boot mode with our SK7 board and it works fine. For our final hardware we will add the following solution:
Our devices have always a reset button (or power on will work as well) and we are going to connect one of our user buttons additional to the MD pin. For updating, the user has to hold this button pressed (pulls MD to GND), then he has to reset or power up the device to set the S7 to USB Boot mode, so there is no need to open the device. I've tested this scenario with the SK 7 and it seems to work.
Best regards
Ralph