The problem with this logic is that no where does a merger policy talk about "lifestyle expectations." It only talks about career expectations, which is much more definable than lifestyle which is infinitely subjective. The difference in your example is that the 170 captain has no where to go. (Unless he was recalled to mainline.) The 737/A320 f/o can only go up. The other direction is furloughed.
Those of us who came up from commuters generally left our former employers somewhere near the top, with schedule, equipment, even pay, to take jobs on reserve at the bottom with less pay at our current employer. If lifestyle was such a factor, why on earth would we do that?
A mainline job is a mainline job no matter how you slice it. And at US the only way to get that back was/is a recall letter.
Let me ask you this? Did MDA pilots work under the same contract as mainline? Of course not. There goes that quality of life thing again. Hours or service, guarantees, vacation days, call out time, duty rigs, monthly caps, etc. etc.etc. Since when is flying for a commuter, even as a captain considered a quality of life improvement? ANd the separate contract is another factor that works against you, pointing once again to the fact that MDA was seperate from mainline. At UA with Ted (and DL with Song) pilots worked under the same contract regardless and could bid on or off without restriction. Same contract, same work rules, same quality of life.