Ryanair's latest idea.
I'd love them to go ahead with it. I can see me on their flight, deliberately not having any pound coins on me, so as not to encourage them, standing with a small child peeing on the plane floor because I don't have change for their loo.
Most of all I am desperate to see it backfire. I want to see their faces when people finally stop buying their ridiculously over-priced in-flight drinks, for fear of needing to pee before touchdown. That'd just make my day!