No player should be untradable if the deal will improve the team.
Pierce is the closest too it since he's been a Celtic his whole career and been a HoF player for us. But even then if it'd get us close to another banner, you have to think about it!
For a player who's only been a C for two years, of course you have to see what you can get.
While that's a good idea in theory, I'd argue that the Celtics can be so good next year with the team they have that there's no trade out there (within reason) that would unquestionably improve this team.
Could we get players who on paper might seem better than Ray and Rondo?
Maybe.
But there's no guarantee that those players that are better on paper will make the team any better. There's been plenty of talented teams over the years that simply didn't gel.
This team won 66 games 2 seasons ago and won 62 games this year, while KG missed 1/3 of the season. During that time, Rondo and Perk have blossomed. Add a healthy KG, even more improved Perk and Rondo, plus a couple of bench pieces, and I think this team can win 70+ games.
You don't break up teams that can do that with the pipe dream you might be able to get even better. It'd be like winning the lottery then going to Vegas. You could win more money, but you're much, much more likely to lose it. We've already won the lottery, we don't need to go to Vegas.