Thanks a lot for your answers. You motivated me to continue on the sprite.
First I changed the palette in the flat-shaded version:
new <-> old

I think it's a mixture between A1 (old) and A2.
Then I was motivated to continue on a full-shaded version of the sprite. First I tried to reshade it on a pixel level, but I completely failed. Therefore I painted a big version and resized it and cleaned it up at pixel level:

resized+cleaned up <-> old

I think I like the newest one the best (from the full-shaded ones), but I believe it still looks resized. I not sure why, tho.
What do you think?