LH Lisa
Lack of control in the work place has been linked to coronary disease, muscular skeletal disease, negative mental health outcomes, fatigue and other medical conditions. Junior crew suffer from a distinct lack of control in their workplace.
I would love to hear your sources regarding 'muscular skeletal disease' [sic] being attributed to a rostering system. By the way,you might prefer the term Musculoskeletal disorder/disease,as it is the recognised diagnosis,rather than the one you described (which actually doesn't exist).
I believe I work for the same airline as you,if so I am junior to you. I have never seen crew meals chosen on senority,have never seen rest breaks chosen on seniority and the only difference I have ever seen in hotels is CSMs and Captains sometimes get upgraded rooms at some hotels.
I love my job,the freedom it gives me,the travel I get,the great people I work with/meet and the great pay for so few hours actually worked. Yeah I don't get anything I bid for and am at the bottom of the onboard work choices every time I go to work. I dont care either way,what does it matter?
Easy choice for you,if the seniority system is causing you so much grief, drama,mental health problems,'muscular skeletal disease' [sic] etc etc etc etc etc etc etc etc etc etc etc etc etc (the list seems endless for you)
Just leave! Or go to another division in the company that doesn't have seniority based bidding (of which there are now many).
The job obviously isn't for you, we all know what we signed up for. If the majority of cabin crew who are in the seniority system want to keep it then it will stay as it is.
And comparing it to
Apartheid ? Are you f*cking insane? This is your
JOB,not your
life. Comparing anything as inconsequential as where you work on a bloody plane to Apartheid is probably the most stupid/thoughtless/self-obsessed comment I have ever seen/heard from a cabin crew member. Those who live/lived under Apartheid do it for
EVERY SECOND OF THEIR LIFE 
No wonder everyone thinks cabin crew are just brainless waiters in the sky-LH Lisa you have given evidence to support the public's opinion.