I absolutely would trade for "Mini LeBron" at the expense of Smart.
Bledsoe is still a bit too turnover prone, but he really does it all. He's greatly improved his shooting over the past few years, has proven he can work in tandem with another PG on the floor, doesn't dominate the ball, and is perfect for an up-tempo offense.
It's acquiring guys like Bledsoe that is going to lead to free agents taking a hard look at Boston rather than a passing glance.