I was surprised to find out that this was one of the first pieces of humanistic art to come from the Renaissance, but it being a biblical reference makes sense. The uncommon depiction of David is very interesting and Donatello certainly had his hand in the form of the sculpture. 
Donatello's David should be preserved, but I feel it's importance is in it's context as a comparison with other Davids of the time and who commissioned it. The history behind the art is as important as the art itself. 
I want to ask how important you think Donatello's possible homosexuality is in the interpretation of David. You mentioned earlier that the Medici's possibly commissioned him to depict David this way, so I would like clarity between the motivations.