Just because Smart can't shoot, that doesn't mean he won't fit well with Rondo. He may not be a shooter but he is a good at creating his own shot by attacking the basket and bully his defenders down low. I believe he can also play off the ball and already an elite defender.
There's our perimeter big guys that can stretch the floor and Smart is a very good rebounder for his position.
A guard rotation of AB-Rondo-Smart will be a nightmare defensively for opposing teams.