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.

From November of last year:

Ryan Doumit, Nate McLouth, Paul Maholm, Matt Capps: These four are described as "as close to untouchable as it gets" for the Pirates.

http://www.mlbtraderumors.com/2008/11/pirates-rumors.html

When the Bucs could have had multiple teams interested at the same time to get some competition for him, they shut off discussion.  But come June 1, they take what I assume to be the very first offer from the Braves.  The Yankees were looking to make a big push for McLouth last year, and they always are liberal with their prospects and young talent.