I realize it's not your character. What I meant was that I think you should offer to improve on the design since it can reflect poorly on you if people associate someone else's bad character design with your work. If I had your talent, no one could pay me enough to draw a character like this. They should trust your expertise if you explain that the character is badly designed.
I think the execution of the art piece is quite favorable, and I like the design, regardless of who designed it. Everybody has different opinions of good and bad character design. If the person who commissioned the piece is pleased, then that's the important thing, especially if it's for an original character.
Anyway, just wanted to say nice work, on this and all your pieces.