I think Green would be a great fit, but I wouldn't want to give up Williams, Williams, or Smart to get him.
I don't think Langford, Theis, and Kanter quite gets us there either, either from a salary matching perspective or a value perspective. That means we would need to send 4 players, but 4 for 1 trades are pretty rare in the NBA. Smile or Pascal would have to come back to the Cs.
Then its just an issue of value. The Cs can give the Memphis pick and the Bucks pick. That gives the Warriors a ton of draft capital in 2020. I'm guess the Warriors would require Williams, Williams, and/or Edwards as part of any deal. That would be a sticking point with me, but probably not enough for me not to do the deal.
Green provides an answer to Giannis, Simmons, and Horford, and provides a little help with Embiid (especially if he refuses to stay in the low post). Green, Williams, Smart, and Williams can do all the dirty work as low usage defensive playmakers and smart offensive players who can all pass. Walker, Hayward, Brown, and Tatum can be the offensive playmakers. Poirier, Edwards, and Wanamaker can all be deep bench options.
If you put Williams in the dunker spot and run pick-and-rolls with Walker-Green, Green would give a lot of alleyoops to Williams too.
It really makes a ton of sense for both teams.
HOWEVER, I don't think we should mess with the team chemistry at all right now. We've got a good thing going. If Brown and Tatum continue to go to the next level, everything changes in our team needs (for example, the Clippers have Harrell and Zubac inside--that's not a daunting front court). There's a good feel going on right now. We probably need an answer eventually inside, but I'm not sure I would seek that answer in another prickly player like Green.