The thing is, the Celtics don't need it to be a great first rounder, have you looked at the list of picks they're owed?
The 2015 draft they get the Clippers and Heat pick, Heats pick is only protected 1-14 and they will make the playoffs.
Next year and until 2018 they get the Nets pick.
In addition to a gang of 2nd rounders.....They don't need the pick to be great, they have their own top 10 coming this year.
We don't have Miami's pick, we have Philly's pick that's lottery protected and since they aren't making the playoffs it'll turn into two second round picks.
Danny Ainge can do whatever he wants, but at the end of the day there's no incentive or upside to trading Rondo for some expiring veteran backups and some meaningless late 1st rounders.
Put it like this, I think damn near every other team in the league could offer a more enticing package for Rondo than the Mavs could. That's how bad of a trade partner I think they are with the Celtics. They have nothing of substance to offer. If Danny Ainge were to trade Rondo for that Mavs package I'd just assume that they were the only team that had an offer on the table.