I'm not a fan of trading McCutchen or Harrison.
Yeah, the Pirates will eventually trade McCutchen, thus is the way of the small-market team in the Majors. There's little point in selling when his stock is at an all-time low. Give him a season to bounce back, then make a move next year. It makes way more sense.
Honestly though, moving McCutchen makes more sense than moving Harrison. The Pirates don't need to lose another starting position player. At least if McCutchen is traded they can easily move Marte to CF. If they trade Harrison, who's going to replace him? Alen Hanson? Adam Frazier? I like both players, but as utility guys, neither are capable starters at least this point in their careers.
The only possible move would be to move Kang to 2B then have Freese as your starting 3B, but even then it's a downgrade. Keep them both, the Pirates have luxury items like Freese as a bench player but don't have the basics like a solid pitching staff. Once they acquire a solid third starting pitcher then they can focus on other aspects. Defense and pitching is what screwed them over last season.