Sure, the old jobs don't come back. TYhe new jobs tend to be crappier than the old jobs due to employers taking advantage of desperation (a form of rent seeking)
People flocked from the farms tot he factories during the industrial revolution in the US because those jobs were better. Exactly the same was true in China much more recently. Early manufacturing jobs paid very much better than anything else around. Sure, they were very exploitive by today's standards, but so was everything else at the time. It was only as time went on that workers wanted more (generally it was more about working conditions than pay early on).
Training programs and strong unemployment benefits that actually support the displaced workers while they learn a new skill would be one aproach, but it would need careful controls so it didn't take part in pushing workers into crappier jobs.
Sure, in fact I have a hard time imagining how it could lead to crappier jobs, unless we brought back indentured servitude (aka, non-compete agreements). When you have no skill, you're completely replaceable so your employer has all the power. When you have a skill, well, ever try to get a plumber in a hurry? You know who has the power there.
The basic income is probably the strongest approach. By taking poverty off of the table once and for all, the workforce gains sufficient bargaining power
Complete disregard for human nature. The basic income produces Chavs, not skilled workers. The experiment's been repeated many times: people who don't have to work don't work, and produce a culture of "work is for suckers" that's quite difficult to escape. I spent many years living in what passes in America for poor areas, and the patterns that kept people in poverty were clear once you started to know your neighbors - either a firm belief that "work is for suckers," or a hard worker coupled directly to a leech (and somehow it was also the woman busting ass and the man laying around all day). Causation is just my opinion, but the patterns were self-evident.
Giving people money for not working is a social death trap. Giving people education to become skilled workers also gives them lots of power. (Seriously - try telling a plumber the kind of shit that developers get told about what tools to use or whatnot, and see how far you get! Skilled blue collar workers are less replaceable than skilled white collar workers - though of course we should provide education leading to either sort of job to all.)
give them good reason to believe they can transition painlessly to new and better jobs In fact, they might voluntarily sign up to lose their old jobs.
No argument there.
Keep in mind in your calculations that the union victory on the 8 hour day and 40 hour week had a lot to do with getting people employed as well
Have you never been poor or worked shit jobs? There is no 40 hour work week - you work 30 hours at each of two jobs, and have to add a second fucking commute to your already-long day because some goddamned do-gooder thought there was a 40-hour work week!
OTOH, if we have a social change, a change of common expectations of people, that 30 hours was a good work week (or 40-50 hours in your 20s, but 25-30 once you master your trade), that would be great for everyone I think.