I just think you're underestimating the economics of the NBA a little.
I think dumping Wallace or Gordon would cost a lot more than a #2. It cost the Warriors two #1s to clear space to sign Iguodala, for instance.
Similarly, taking on $15 million in salary for a decent -- but not blue chip -- prospect seems like a lot to give up.
Let's say that $15 million in cap space is worth two #1s (again, based on previous value). Let's call Green worth a #1 (although probably one in the bottom third of the round).
That's the equivalent of giving up three #1s (plus taking on Rivers, who I think is useless) for Barnes.
That's interesting, and you make some great points, but I think you are presenting a best-case scenario for a return on cap space and Green, which is both unlikely and time-sensitive.
Though probably worth it, at least in a vacuum, Green very well may not fetch a first-rounder (particularly on an expiring contract, in essence), and we may likely get nothing for him. I think it's wise to fish around for the best offer, certainly, but we need to take what we can get rather than let him walk.
Dumping salary is most costly when in a pinch, such as GSW in your Iguodala example, or CLE when we took on Thornton (to accommodate the signings of Love & Lebron). These teams were at their most desperate and willing to part with a little more. However, increasing cap space across the league devalues each team's particular cap space, and with projections of enormous cap increases over the next couple of years, it seems likely that cap space will be further devalued accordingly. Additionally, I think PHI is a unique example right now, as they have more cap space than they can use, and they are hungry for assets. If BOS, whether right now or during the 2015 offseason, offered Wallace to PHI plus their 2015 2nd rounder, I think they consider it. If we threw in the DAL 2016 2nd rounder as well, I think there's a good chance it gets done. Now, if BOS's back was against the wall (like GSW w/Iguodala, or CLE w/Lebron&Love), PHI may rightfully and successfully hold out for more. But if we held firm with that offer, I think PHI would be too tempted to balk at extra assets in exchange for cap space they wouldn't otherwise use.
Rivers may indeed be useless, but I think he is improving and worth a gamble. I think Ainge likes Rivers as well, although that is obviously no indication he will turn into anything useful.
Both Barnes and Rivers seem more promising to me than another late first-rounder or two anyhow, especially since we will have nearly enough first-rounders as is to field a 2017 all-rookie team.
