Pass-A-Frodo, I have to take my hat off to you. While I think it's creditable that you don't spend Friday night glued to PPRuNe - I'm suspicious of your statement, because of the obvious effort involved in dragging down that text book, finding the supply and demand curve, and somehow importing it into this thread. Well done. But it does smack of too much effort.
Unfortunately, it further supports my contention. You are supply side obsessed. Your chart shows the effect of an isolated increase in wages, acting through constant supply/demand equations. It does not deal with changes in the curves themselves. You are clutching at fancy straws.
I have long held the view that unions exist because they need to. Or, in other words, Companies that deserve unions get them.