My thinking is on those lines, Sandy.......an ID card system for alcohol up to 25. 3 strikes (perhaps weighted to the seriousness of the offence) and you are out ré buying booze. And make it a much more serious offence to be caught supplying underage or banned people alcohol....... a sort of driving licence in effect.
No system is perfect and sure there will be flaws to the above, but clobbering those who respect alcohol, to me, is nuts. Any other ways of achieving a modicum of control out there, rather than trying to machine-gun suggestions?