With two max guys already on the roster, and most likely a third after next season with Thomas, the Celtics need to hold onto their young talent to help with the salary cap (Brown, Tatum, 2018 draft picks). I don't see Danny or ownership, having any desire to trade any of those young assets.
I believe the best package the Celtics could offer is still Thomas, Crowder, Rozier, and the Celtics 2018 own first round draft pick. Having said that, I'm not sure if Boston would even do that deal. Trading Thomas would be very difficult, as Thomas has built up so much good will amongst the fans, teammates and ownership. As discussed, there isn't much of a statistical difference between Thomas and Irving, so I think intangibles have to play a factor, which is where I believe Thomas clearly has the edge. Also, Crowder is a strong role player that most playoff teams need (who also helps with the salary cap issue)
When it comes to evaluating Irving, I don't think you can rely on statistics to measure him against Thomas. Were Thomas' numbers over inflated because Boston had no other reliable #1 or #2 scoring option? Were Irving's numbers under inflated because he was playing with go to scorers and elite passers in LeBron and Love? When it comes to evaluating who is a max player, I wouldn't hesitate to give Irving one of those contracts. However, I still do have concerns about giving one to Thomas.
Danny and Brad are in a tough spot. I believe Irving is the better player, and the Celtics have the assets available to make a trade. However, do the ends justify the means?