Adding Rondo in place of Turner wouldn't help us in any of the areas in which we are weak, and it would weaken us in areas in which we are strong.
Personally, I'd like to see him head to New York to throw lobs to Porzinger.
We have lot of weak areas. Rondo is a better game manager than either Turner or Thomas (at least for the first 3.5 quarters - tends to self-destruct in a big role in the clutch with his FT and shooting issues).
That's not so important now, but if we actually had real offensive players to set-up and not just a bunch of defensive role players who let IT and ET play-act as #1 options than that weakness would become much more problematic. Turner in particular has always struggled to play with major offensive talent and IT's no saint in this regard (ditched by Sac and Pho for just this reason)
I think a Rondo/IT dynamic could work very well offensively. A great ying-yang. Rondo as the Jason Kidd game manager, IT as the JET closer.
Of course Smart could turn the corner as a playmaker (he's already got the unselfish facilitator mindset down, he just needs to actually create something) and make this conversation moot, but I'm not convinced about that. Seems to be settling into a strictly secondary playmaking niche.