Problem with "making trades" is that if you have multiple 1B only types, it's hard to get them enough credible PT to make them viable trade chips.
Say if Hoskins or Joseph could play LF, you could put them both in the lineup, showcase them, and take your time moving them.
But with Joseph at 1B, Hoskins is trapped in AAA, because you're not going to increase either player's value by having them split time at 1B in the majors.
This is also a problem with Hernandez/Kingery, since both are 2B only, again, once Kingery is ready for the majors, you have fewer options.
Whereas as we've seen with Altherr, he can play all three OF spots, so he doesn't block anyone.
A lot of making a good trade is being able to wait until the right deal comes along. That's easier if players are flexible.
So flexibility in and of itself is a "skill" in a prospect.