I get the premise. In an ideal scenario, Noel comes in and gives the Cs everything they need up front to go along with Horford. When the off-season comes, we extend the QO to Noel giving us the option to sign another big name FA (I don't think you could do KO and Noel in this scenario, though). This is the benefit of acquiring him via trade rather than throwing $20M+/yr at him in FA - it doesn't eat up nearly as much cap space.
In addition to Noel, you hope to get a top 10 pick from LAL to replace Brown and also have the back-up SF minutes solidified by a productive player/shooter in Covington.
I have no doubt that we would be better this year with this trade, but it is also the type of trade very few gms end up making, due in large part to the possibility of what Brown might become. I wouldn't freak out if this deal was made, but I would then have to totally root against Brown forever, which I wouldn't like doing.