Most of the players mentioned as needing to go are expiring contracts. Rondo, Green (by virtue of player option), Thornton, Bass, and Anthony are all expiring and total about $41M. I think it is very likely that none of these players will resign with the Celtics after what is likely another bad, rebuilding season.
So there are two options; one is let them all expire and plan to sign other better FAs to replace them. Or you trade some or all and get what you can. I don't think the prospect of attracting or retaining FAs is going to be very good after this coming season (rock). I also think that for the most part (excepting Rondo), the trade value of the group is pretty low (hard place).
So by my calculation, the best bet is to trade Rondo (since we can actually get something for him) and let the rest expire since what we would get back probably is not going to be all that good anyway. I guess DA will try to trade any of them as he should but no trades just to trade.
I think Evan Turner is a good example of a low cost, short term contract player with some potential upside. Trading for that type of situation would be fine with the Bass/Thornton/Anthony contracts but I don't see that many cases for that type of trade. Rondo should be able to get us some decent value back and Green somewhere in the middle.
Your points are valid but I don't see why the C's would trade Rondo when they are trying to draft/develop players his caliber.