That's a tough question, because I would start with the drummer. The only perfect candidate is not available.
Next, why doesn't Matt sit right with me? I don't think it's his playing, necessarily; I think it's the production. Listen to "There Goes God" from the live CD and tell me you've ever heard anything remotely like that from Matt. Given the sound of everything in the last 10 years, I have to believe that's all Neil's choice.
That leads me to believe that Neil doesn't want "Crowded House" to be "Crowded House", and so we have to either accept what he does want, or just listen to our old bootlegs.