I agree with this. I suggest taking a look at how they make sock liners in your shoes. That is the padding that separates your foot from the upper material. I think it should be fairly game accurate in appearance as well if stitched properly. I don't recall the in-game model looking like it had a leather liner but I could be wrong about that.Easiest way to make the padding would be to sew 3d-spacer mesh over foam, then either mechanically attach that to the hard inside part, or velcro it in place.
Also, this project is amazing. It definitely ticks all the correct boxes for me.