Does it (a PhD) truly equip you for the job ahead or is there an element of making people do it the hard way?
LOL at this question. I think you have to want to do a PhD to spend three years on it, rather than it being a means to a job in a university. Having a PhD does not guarantee you a job in a university either - there are lots of good people on temporary contracts, because that's just the way things are at the moment.
But I think a PhD does equip you for the job nowadays because, as I said before, so much of the job is research-oriented, getting funding, carrying out projects and publishing. The whole PhD experience is about very much more than just doing a piece of work and writing it up, you are expected to do postgrad conferences, and publish from your thesis if you want a good job. Of course it is possible to take the research associate route, and that equips you just as well, but certainly, in my experience, you would be expected to be studying for a PhD as well.
As to whether a PhD equips you for teaching, that is harder to answer, because you would also be expected to do some kind of new lecturers course. But as courses are expected to be up to date, then you have to be abreast with developments in the field, as well as the literature. I'm too tired on a Friday afternoon to write the whole transferable skills piece that your question demands, but yes, in general, I think a PhD (properly supervised within a thriving research community) gives you a good grounding for academic life.
As to the second question, I don't think there is an upper age limit for a career change, though some funding bodies do impose one for PhD funding!
LOL at the length of my answer, sorry. I'm going back to work now....