Looks great! I built a controller recently too, just wanted to mention that I used the open source GP2040-CE on a Raspberry Pi Pico and it works great, it involved a bit of soldering wires with different connectors together, but there are now custom RP2040 controller boards that can run it and are plug-and-play.
I tried to play Ultra Sun using only my starter Rowlet, and had to put it down when the game forced me into a double battle. I would have been okay with hatching a second Rowlet from an egg but it didn’t work.