I think that classes should not be extended.
Extension of class causes various problems.
There are some patches to fix it, but it is still hard to make it work perfectly.
I think that the merit obtained when expanding the class and the risk that occurs when extending the class are not now balanced.
There are too many risks.
If you absolutely want to class extend, I can not stop it.
However, You have to fight with various problems.
The save data extension of FEBuilderGBA "class_fix" is based on the script of kirb.
Something might be wrong with this script.
But I can not do anything.
It is difficult to support because I did not make it.
I made a strong warning when expanding the class.
Still, some people are experiencing trouble by extending the class.
I would like to consider hiding class expansion buttons by default....