With respect to Phil being willing to trade Melo within the division: that is obviously a drawback to dealing with the Celtics (from PJ's perspective). But is that negative mitigated at all by the prospect of succeeding off of the failure of a division (and city) rival?
Envision the Knicks turning around their franchise on the backs of multiple lottery picks...lottery picks that originally belonged to the Nets. So while the "little brother" is suffering, the older brother is turning his lottery picks in to stars.
To me, that would be a huge deal for the Knicks, but would that possibility be worth the certaintly of trading Melo to Boston? Especially if ours is the best offer anyway, and the only thing holding Phil back is the division rival aspect of it.