Absolutely fantastic job on this! Looking forward to the planned Mii NPCs, as they'll make the island feel more lively.
I'd love an auto-dash feature, where the Mii runs automatically and you have to press Shift to walk. The walking speed is quite low, so I always run everywhere, but it tires my hand a bit to constantly hold Shift down on my keyboard. I also wouldn't mind a slider to change the volume of the swimming sounds, as the "fast swim" sound gets a bit grating to me after some time.
Overall this is an incredible and highly polished program, you're doing great work here!