I'm not 100% sure where I'm going with this - so hear me out.
What about trading the Brooklyn pick but adding protections on to it? It's a bit of a gamble, but will let us trade for some of the lesser talents that people have been discussing without giving up on getting a Porter or Bagley.
Some examples:
Type 1: Decreasing the value of the Brooklyn First:
Cavs trade: Shumpert + Brooklyn First (top 3 protected, reverts to Cavs 2018 1st and Cavs 2020 1st if Brooklyn 1st is in the top 3) for Kris Middleton.
You can put just about any name in place of Kris Middleton there (with almost any team). In this case, we get a premium shooting guard to help this year. Milwaukee either gets two first round draft picks, or they get a Brooklyn First that is probably in the 4-10 range in a stacked draft. The Cavs get a player that can help this year, and don't lose on the chance to get a premium talent.
Type 2: Trading with Brooklyn (this is a bit wacky):
Cavs Trade: Gives Brooklyn the following protection: If the Brooklyn pick is Top 2 then Brooklyn gets the 2018 pick, and the Cavs get Brooklyn's 2019 pick instead.
Cavs Get: Rondae Hollis-Jefferson
Here we again pick up a young wing defender, who could be a piece going forward. Brooklyn should be looking to tank this season, and now they can try to do it. It basically moves Brooklyns timeline forward by a year. Conversely the fact that Brooklyn is trying to tank really increases the chance that their pick is in the 3-5 range, which helps the cavs a bit as well. At worst, the Cavs timeline gets pushed back a year when we get an extra Brooklyn first round pick that should be in the mid-lottery.
Type 2b: Trading with Brooklyn
Cavs Trade: Brooklyn 2018 First Round pick
Cavs Get: DeAngelo Russell, Rondae Hollis-Jefferson, Brooklyn 2019 First round Pick (unprotected)
Again, Brooklyn goes into full tank mode this season - with basically no talent left on their roster. Cavs get some pieces for this season (maybe send Russell somewhere else for a late first?) And the Cavs still have some insurance in the form of extra picks if Lebron leaves.
Anyway - there are a million permutations of trades like this. My point is that it is possible to change the value of the Brooklyn 1st to match what you are trying to trade for -- just by varying the protections in the pick.