Trading Lopez has some built in contradictions. The Nets would want good young players and high potential future picks. Any team that wants an established player like Lopez, is probably at least half decent and looking to get better. Lopez will make the team better and reduce the value of the future picks that the Nets get back from that team. A bad team with good future picks isn't going to want Lopez.
That is why I think the Celtics should try to make a trade. Give the Nets back their 2018 pick while keeping the 2017 pick. Then the Nets can tank through 2018 and make sure it is a valuable pick. The Celtics can include Amir, one of our stashes, and perhaps another future pick. A good deal for the Nets. They won't do better than that.
The Celtics can see how we do with Lopez paired with Horford up front for the season. I would assume Lopez would play well and we could decide to continue to build around Horford/Lopez or trade one or both and go a different direction.
I like this trade because it protects the 2017 pick by making the Nets worse and provides a hedge against the Nets getting good and lowering the value of the 2018 pick. I think we end up flipping Lopez but in a best case scenario, he helps us get someone like Cousins.