Would Delwyn Young, Eric Hinske, or a mix of both make more sense in left field than Nyjer Morgan for improved hitting and power, or would it take too much away from the Pirates in speed and defense?

I'd suggest Steven Pearce as well, but he probably couldn't handle the outfield at all if he has been at first base or DH the entire season.

Moss has been a similar no-hit, great field player thus far, but at least he has power potential and is young with room to grow.  Morgan has none of that, and for all his speed he can be a sloppy fielder and baserunner.