I like Brad Smith returning kicks -- he's more than adequate in that department. And I'm not concerned one bit about him taking a pounding. He's the 4th WR/gadget player. If he's not returning kicks, he doesn't have a whole lot of value.
Regarding Leon: If he's not healthy enough to return kicks, he's not healthy enough to play. Period. He's a dynamic player in the open field, and if his injury is significantly limiting his explosiveness, he's worthless.
As for punt return duties, that is something that needs addressed. I would like to see what that CFL guy can do, but he has to be able to do more than just return punts to have a spot on the active gameday roster. That should also be Leon's job if he's healthy enough. Maybe Brad can return punts, too. I wouldn't count on it though.
I have a feeling that they are going to draft an offensive playmaker in the 1st 2 rounds -- that guy might also help in the return game.