My preferred method is to weight votes according to age: voters below, say, 30 would receive a more heavily weighted vote, voters 30 to 60 would get a less weighted vote, and those over 60 would retain their current single vote. For argument’s sake, you could multiply the vote of under-30s by 1.3 and that of 30- to 60-year-olds by 1.1. People’s ballot papers could be distinguished by colour – under-30s get blue, 30s to 60s green and oldies red – to make counting easier on election night.
With respect, that’s exactly how they currently change things. By legislation, so they most certainly could change the weighting as easily as they can pass any other legislation.
What I meant by not changing such legislation easily is that it would need to be debated and the public would be able to also have a say.
I’d certainly be interested in seeing something like this be given a trial run for 5-10 yrs to see what outcomes would eventuate.