Connecting a few of the dots here, would it not be the best idea to have weighbridges for aircraft in taxiways in order to (a) give the takeoff weight to the captain for thrust settings (b) charge the airline a tariff for TOW, and (c) give a checksum for any irregularities between the expected and actual weights that could point to something awry (such as ice on the wings?)
If they're charging based on takeoff weight and Ryanair saved millions, then the cost of a weighbridge pales into insignificance just on that saving alone, let alone the savings in lives and money from incidents based on false TOW.