I think Ryanair are going to find themselves in serious legal trouble if they try to implement their extra charges for men over 130kg but women over 100kg (or for men with a more-than- 45 inch waist but women for a more-than-40 inch waist): it’s normally not legal to announce that women and men will be charged different prices for the same service. They may also have a difficulty with BMI, as women and men vary on that so that a court may find that this is effectively sex discrimination even if not explicitly so.
They may be able to charge for a second seat if a person doesn’t fit into just one (their fourth option) as that’s their only non-discriminatory option: but I noticed in the news that a Canadian court has ruled that in fact airlines simply have to swallow the cost of an extra seat, if they choose to provide seats that are too narrow for their customer base to fit into.