Hi! I'm the author of miniMAXIme, and supplied the code that made SleepyEngi's Gear Girl not overwrite the default character. Meanwhile, it has turned out that my original approach to creating characters wasn't ideal (e.g. Gear Girl is still overwriting properties that other mods may have changed), so I've made several improvements to the process over time. Unfortunately, it seems SleepyEngi has been asleep for some time, so these improvements never made it into Gear Girl. :-)
However, I've also made a helper mod that provides some functions to help you create your character and handles copying it from/to the default character. The mod contains example code and documentation, so if you want to take advantage of it, it shouldn't be too hard to make the necessary adjustments to your code.
By the way: I've also added an optional dependency on your mod to the next version of miniMAXIme, but it may still take some time before I'll get around to updating the mod again.
EDIT: Just uploaded version 1.1.29 of miniMAXIme with the dependency on your mod.