My opinion: Point guards don't win titles. Big men do.
And yet you want to sign Deron Williams to a max contact. 
That's an idea. I like Deron over Rondo, because Deron does everything Rondo does... but is bigger and a far better shooter/scorer. Deron is just a better player. Period. Obviously wouldn't be the end-all move. You don't simply win a title with Deron Williams by himself and you sure as heck don't simply win a title with Rondo by himself. But you're leaving out the key part of my Deron Williams pipe dream... if you signed him to the Celtics you'd then be able to move Rondo to the highest bidder. Ultimate fantasy is landing Dwight HOward for Rondo, both our first rounders + whatever else Orlando wants...
Also the only reason I mention Deron is because he's BY FAR the best unrestricted free agent this offseason and we happen to have cap space. If our MVP Kevin Garnett retires... I'm not sure how else we could make an immediate impact this offseason.
Sure Deron Williams does everything Rondo does, but Rondo does quite a bit of it better like passing, rebounding and playing defense. Williams shoots better from the perimeter and scores more points.
I don't know if you find playing D, rebounding, and passing to be irrelevant, and shooting the basketball to be the only skill that has any significance, but it sure seems that way.
I disagree that Rondo is a better passer than Williams
If Deron has 3 hall of famers on his team, or even more capable players than his Nets teammates, his assists would go up too. Rondo's passes are just more flashier
But how does that (3 HOFers) explain the various lineup shifts that Rondo has had to deal with since the beginning of March?
I mean - Rondo didn't even have Ray for most of April...he even lacked Paul and KG for a few games, if I'm not mistaken?
Without going into too much detail, I know for a fact that he's had any combination of AB, Paul, KG, Hollins, Stiemer, Pietrus, Bass, JJ, E'Twuan starting since March...even ALL SEASON....we've had SO MANY different patchwork lineups that Rondo has had to deal with.
And he's dealt with it WELL, to say the least. The good times have rolled to the tune of what 24 straight 10+ assists games?
No matter what our lineup has looked like, Rajon Rondo has been steady. He's been our constant. He's dealt with those lineups professionally, for the most part, and adjusted to it.
Like Magic Johnson stated - Rajon Rondo has been the best PG in the NBA this season.
Magic knows his stuff.
Rajon Rondo IS a better distributor than Deron Williams...and is quickly becoming a better overall player.
I heard one of the ESPN analysts state last week that Rajon has been practically bumping shoulders with CP3. That is good company.