Modding

Another question is how feasible is its creation from a technical point of view?

Technically, it is 100 percent feasible.
From the point of view of writing the program, as far as I understand, there is nothing complicated, because all that is needed is a program that simply makes changes to text files and changes the arrangement of images in the user interface.
From the point of view of preparing resources. Cutting a bunch of original hero models into pieces is also not a difficult task, however, it was probably time-consuming and very tedious.

Is it really possible to make the interface understandable and simple?

You just need to make something in the spirit of the customization interface that exists in many games. Just a concept.

If someone skilled could implement this, I am sure they would not be at a loss.

I don't quite understand what is meant by "not at a loss".