Justin Jackson & Georgios Papagiannis for Porter would be something I would do.
I'd also take back Gortat & Smith with a 2019 1st attached to help them create more cap space. (still allows us to maintain cap space in 2019)
I think another interesting deal would be Bradley Beal, Ian Mahinmi, & Markieff Morris for D'Angelo Russell, Trevor Booker, Justin Hamilton, & Isaiah Whitehead. That would basically take off all of their long term deals, give them young assets such as Russell, Oubre, Jackson, Papagiannis, & their own 2018 1st around Wall while having about $57 mil in cap space during the 2018 offseason (which they can use on Cousins & other FAs).
I don't know. I think this is way too much to give, and for what? We aren't making the playoffs this year, or even next. We have to see how some of the kids develop. As for Porter, we haven't seen him in action as the main guy. Will he be as good without two all stars sharing the floor with him?
Look at what Bulls got for Butler, or Pacers for George. Yes, there were some constraints, particularly in George's case, but both are established stars in the league. Porter is not in that category, at least not yet. Plus, the Wiz have problems of their own. If they retain Porter, they almost certainly lose Bojan. Even now, they are at best the third team in the East, and face competition from Raptors for that. Once they are capped out, they are stuck where they are. If Philly does make a jump, this year or next, they will lose that position too.
It can be argued that Both Jackson and Papa haven't proven anything yet, and trading them to get an established player is worth the trouble. Possible. However, trade value of stars seem to be lower than we think. We ourselves didn't get value in Boogie's trade. It's possible that either of them (or hopefully both), show big improvements, and play on rookie contracts for few more years.
It's quite likely that some teams that have signed the rich contracts now, will be willing to move these, or some other piece to get under the tax. We will be one of the few teams with cap space, and we can hopefully use it to our profit. I know we have been hoping for this, and have not seen the results yet. That said, the high amounts being offered, and the level of competition (particularly in the West) will force teams to evaluate their salaries and taxes wrt to their making a deep playoff run, or even make the playoffs at all. There will be trades available by the deadline. I feel there is no need to be desperate and give up too much for Porter. If he accepts our offer, and Wizards refuse to match, great. Else, we sign some other vet to provide help at 3, and wait to see what deals are available. This year is all about development anyway.