Billups was an asset before he got hurt - was averaging 15/2.5/4.0. Maybe his injury would have occurred with the Knicks, maybe not.
Hindsight is obviously helpful in cases like this, but I agree that the Knicks might re-think the Chandler decision if they had it to do over again.
Don't get me wrong, Tyson Chandler is a great player and was really the only consistent contributor the team had this season, but I'm not sure the Knicks foresaw the effect his arrival was going to have on Amare. He struggled as a 4 this year, and Chandler's presence only intensified the spacing issues that Carmelo and Amare cause when they're on the floor together. Incidentally, Carmelo struggled as a 3 this year. So the addition of Chandler forced the franchise's two most valuable (or at least expensive) pieces into roles in which they're less effective.
But again, I think the Knicks front office genuinely felt that Chandler was a piece that made them contenders, and as such felt that roster flexibility wasn't particularly important. I think they felt like he was the final piece in the building process, and now that that's turned out to be incorrect, have--in typical Knicks fashion--hamstrung themselves pretty badly.
As much as I love Tyson Chandler, I think I'd much prefer to be in a position where Billups, J.R. Smith, Fields, Novak, Jeffries, etc. were expiring AND they still had the amnesty in their back pocket as insurance for Amare. There's a certain point guard across the East River that I'm pretty sure they'd like the cap space to go after right now, and failing that, I'm sure they'd be happy to add New York City resident Steve Nash.
This offseason, they should try to do the following things:
1. Trade Amare. Which is to say, give him away to anybody that will take him. There will be teams with cap space that could afford to take him on and the sheer stupidity of half of the league's GM's provides a glimmer of hope that it's possible. And if they somehow do find a taker, they need to bring in a 3 who defends well to mask Carmelo's deficiency, and make Anthony a full time 4. His PER is substantially better as a 4 than as a 3, and that's just what he is now.
2. Find a real coach. Injuries or not, that Miami series was the most pathetically coached series I've ever seen. Woodson failed to make any adjustments, couldn't get Amare or the leagues best three point shooter shots, and reverted back to his old Atlanta ways of ISO after ISO. It's simply not a winning strategy in the NBA.
3. Try to trade Amare again.
But realistically, this is probably the team they're stuck with. Which is why I think the only real avenue of change involves a new coach.