An Elegant Met Museum Bassoon Reimagined as a Half-Contrabasssoon
Magnificent.
I think you would need to stretch the bottom keyworks upward to make a working instrument, which would also improve the aesthetic balance of this half-contrabasssoon. A good name for the instrument would be "the bumblebee."
In the same spirit, I have long admired the made-up instruments of the artist Donald Evans, who used them on pretend stamps for one of his fictional countries.
above photo from ebay