I think some of these "labor ills" that we are discussing have a lot to do with the nature of museums themselves and much of the non-profit world itself.  Many if not most or all museums have been started by volunteers. We have altruistic missions. We continue to use volunteers  for all manner of tasks so there aren't that many paid museum jobs. There are many waiting in the wings to take any museum job that opens up offering any pay.  
I disagree that museum work doesn't get any "respect."  It may not get respect from the board or other governing body. Those who have volunteered for years and/or founded the museum and put in long hours and donated much money may not respect the work you do. They probably did it differently than you are doing it and they think there way was better. However, people outside of the field seem to attach a lot of prestige to jobs within a museum.
As to whether or not a union will work for the betterment of the museum and it's staff, it depends in large part on the way the contract is written and the way it is interpretted.  I've seen the interpretation twisted to an extent that there was a great deal of difficulty bringing someone from outside into the organization. The results I will leave to your conjecture.

What I suggest is that in order to change the employment conditions, we need to look at a set of standards as to what it takes to be a museum professional.  Then, some how, we need to attach that requirement to "museum" as professional standards are attached to institutions such as "hospital."  Without this we will continue with far more applicants than we have jobs and the resulting ills that we discuss periodically. 

Presently, conservators are in the midst of a discussion about certification.  It won't come easy there or here.

=========================================================
Important Subscriber Information:

The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes).

If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).