Jeff Green is a very athletic power forward with a solid shot and is easily the best out of the five power forwards listed. This is why this is the most unlikely trade scenario, even though his contract is up at the end of this season.
Green is currently averaging 15.5 points, 5.7 rebounds, 2.1 assists, and 1 steal per game. He is undersized but more than makes up for that with great leaping ability and long arms. He would drastically help the Suns and he could easily see an increase in his points and rebounds in the Suns system.
Since he is such an important piece to the Thunder, he would take much more to pry away. I think Hakim Warrick, Gani Lawal, cash considerations, and either a first or second round pick should be able to get Green and probably a second rounder. The one wrinkle is that he still would not have a contract extension and could walk after the season concludes.
The Suns need to see if he is available, and if so, they need to try and do a sign and trade with the Thunder. The above mentioned trade should be enough but you never know since the Thunder are very high on Green.