This trade does not make sense for a team that's leaning towards rebuilding (Even if D.Ainge denies the direction the team is going this coming season).
Even if it were to happen, D.Howard would leave Boston Celtics after a season because he knows he does not want to waste his prime years without being able to contend for a ring.
Also, the situation and offer he's getting from Houston will never be matched by the Celtics anyway.
As a fan, I wouldn't want him on our team.
A High-Risk/High-Reward guy they should be aiming for is G.Oden