Of that list no one is untouchable, as for the right move anyone can be traded, but I know where you are coming from.
I would list Areinamo and Hernandez as the least likely to trade. Jadher can play anywhere, seems to be like a leader, plays solid defense, and may not be a starter in the majors, but is a likely super utility guy who can start and play anywhere and understands the game. If he develops power, and adds a little more discipline (I think that was one of the reasons he was sent back to high A?) then he is more valuable, but worth the gamble given his higher floor.
Otherwise Melvin Hernandez is a huge wild card and hard to value. Is he a legit starting pitcher prospect given how young he is and the success he is having? But his velocity is not there and he can add that as he matures. So if a team over-values his future potential he can be traded, but my guess is his value is low now so probably maybe better to see what we have in him given the long time horizon until he is a higher level prospect, but if a team overvalues him yes sure trade him.
The others are very under the radar prospects, but a guy like Eduardo Garcia who could be this year's "EMJ" as a guy who starts to realize expectations later. Is it because he is a late bloomer, or because he was a little immature (his comments about not taking training as seriously are problematic). There is some power potential and he can play anywhere, but will be a MiLB free agent, so unless he is worthy of a 40 man spot (which I doubt), he is a prime trade candidate. But I do agree, if not traded, he could re-up with the Crew as a free agent to stay here and play with a group of players he has been with and been successful with.
Murray is showing what he can be, but joins a crowded middle infield group that includes Areinamo and Di Turi, as well as the higher end Pratt/Pena/Made, so we will not keep all of them, so a Murray or DiTuri could be a trading chip for an organization that doesn't have as much infield depth.
Kuehner is interesting as there will be a potential log jam in AAA next year (assuming health of course) with Rodriguez, Kuehner, Crow, and likely other AA call ups like Wichrowski, and maybe Cornielle and Hardin, and if a Meyers or Patrick have to be stashed in AAA too (assuming a healthy MIL rotation of Peralta-Miz-Henderson-Gasser-Priester and who knows if a Quintana or Woodruff could re-up with the team). So Kuehner may not have a great path to be a starter here, and could be more valuable to another team which makes his trade value potentially higher, but I still see him staying as the need for a lefty in this organization seems to always exist.