The question should have been simply "Shouldn't we give Marcus the chance to be the starting PG". To that I say yes, that is exactly what I believe the Celtics should do.
Now will he be another Jrue Holiday or Kyle Lowrie, probably not as good as either of these two, or at least not the same. I think Smart as a full time PG will get more assists, play better defense, and bring more intangibles than either of these two but he will not be the scoring threat that these two have been.
And I will go on to say that I am not that concerned with assists. I would rather be the kind of team where there are 3 or 4 players getting 5 or 6 assists each over having your PG get 10 assists and everyone else gets 2. We don't need Smart to be the type of PG that has the ball in his hands all the time. Just get the ball up the court, get the team into something if there isn't a transition opportunity, take good shots when you have them, and make enough of them to keep the defense honest. And get out of the way of the J's when you need to.