Would it be OK for it to choose any terms? Why would it want to choose terms that are different from the govt's already ridiculously overblown requirements? There has to be a rationale for every behaviour and there is too much acceptance of the trite line that it is a private company so it can do what it likes regardless. If anyone can convince me that there is a good reason for them doing something that nobody else (including the governments) requires, then I'll be converted. Until then I'll just assume that it's 'entitlement to choose terms' is a front for something nefarious.
You're welcome to that assumption. Companies are still entitled to prevent anyone they wish from buying from them, and the counterbalance to this is called "the market". If Ryanair's terms were that onerous that enough people chose to do business with someone else, it would be forced to change or go out of business. Last I checked Ryanair is not loss-making.
As I understand it, however, Ryanair's requirement for domestic passengers to produce a passport was implemented so that all their flights would have the same requirement, therefore it could simplify staff training and not have to have a large binder at every boarding gate listing the different kinds of ID that are accepted for different categories of flights.
Again, don't like it? Don't book with Ryanair.
Going to Newcastle on BA isn't a particularly useful way of someone with no ID getting to, say, Dublin is it? Your 'choice' argument doesn't stand up to a lot of scrutiny.
Well, I said someone wanting to go to Dublin with a student card can travel on Aer Lingus. The other items were further examples of how people could avoid Ryanair's requirement that you hold a passport, which you brought up in the first place.