I don't get the argument that Melo and Harris don't fit because they are too similar to each other.
There is no reason why they can't play the 3 and 4 together. Both are versatile players with skill and for every perceived match-up issue one can come up with on the defensive end of the court the Knicks could have a similar advantage on the offensive end of the court.
At 22 I'd certainly target Harris if we could wrestle him away from the Magic. I think Harris fits in with the flow of the triangle and is someone that could be a great 3rd option.